A postwoman struggles with apartment mailboxes as the doorman complains at her. The guy vents that everything in the building is falling apart. Unable to leave the package in the mailbox, the postwoman buzzes an apartment, then gives the resident a package when the resident opens her door. The doorman flirts with the postwoman as she leaves, and then the apartment which got the package blows up.

Briscoe and Logan arrive and learn the victim, now barely alive, was a Florence Manning. One of the police officers on the scene explains that Manning opened up a bomb with a letter opener, and the bomb blasted the letter opener into her neck. Logan finds a remnant of a stamp and the postmark -- it came from Grand Central. The postwoman is there, clearly frightened; she says that she could have detonated the bomb when she tried stuffing it into the box. She doesn't remember any return address. The phone rings, and Logan answers it -- Manning passed away at the hospital.

At the hospital, the detectives talk to Florence's brother, Frank Rossi. Rossi is distraught. He tells them that Florence separated from her husband, Edward Manning, a year ago. Manning works at Hudson University, so the detectives go there.

In his office, Edward tells the detectives that he and Florence were divorcing, but it was amicable. He explains that he's in charge of Hudson University's nuclear reactor. He takes offense to Logan's joke about Chernobyl. He says he doesn't know who killed Florence.

At the precinct, Van Buren snarks to the detectives.

->"I thought no one used regular mail for packages anymore."\\
--Anita Van Buren

Logan thinks it was a random nut who killed Florence, Van Buren suspects Edward. Briscoe reads a press release about Edward; he's a brilliant high energy physicist who discovered a subatomic particle. His research is leading to the conclusion that the universe will eventually decay into nothing. Van Buren sends them to forensics.

The technician tells them that the explosive was plastique, and is easily available on the street. It was a relatively small bomb; the bomb would only have wounded her, but the letter opener was a stroke of misfortune. He shows them a bomb spring and describes the bomb's circuitry. The technician adds that the bomb was well made by someone with technical ability; Logan wonders if a physicist qualifies, and the tech says that experimental physicists would.

At his home, Rossi says that Edward was arrogant and condescending. When Briscoe mentions they suspect Edward, Frank's wife tells them that the divorce was not amicable; Edward slept with a younger woman. Apparently he told Florence that he wanted to marry her. The wife goes on; Florence followed Edward for his whole career, even spending two years in Geneva without any knowledge of Italian. Florence made the divorce as long and expensive as she could.

In an experimental facility, Edward clarifies what he meant when he said the divorce was amicable.

->"You said the divorce was amicable."\\
"I said it was as amicable as could be expected."\\
--Mike Logan and Edward Manning

They ask about the girlfriend; he eventually mentions that she's a chemist and very smart. Logan says that he could have made the bomb; Edward says that he only knows nuclear physics and couldn't build a conventional bomb. He shoos them out of the lab, threatening them with radiation.

->"Our reactor's behind this wall. A shield is being lowered, in order to conduct a diffraction experiment upon that target. I'm going to leave before I'm bombarded with neutrons. I suggest you do the same."\\
--Edward Manning

They talk to the chemist, Cynthia Thomas. She tells them how great Edward is and how important his work is. The detectives pressure her about the relationship; she says that the marriage was on hold, and admits that it's because of Florence. She says that, when she waited in the car for Edward outside Florence's apartment a couple weeks back, she saw a man who was peeping in into the apartment. He argued with Edward once Edward left, but Edward didn't tell Thomas who it was.

Briscoe points out that Florence having a boyfriend would have been good news for Edward as it would have expedited the divorce, so he probably wouldn't have been angry about it, at least not angry enough to send a bomb. The detectives talk about Edward's research, and Logan worries that, if the universe does decay like Edward thinks it will, then there's no meaning in life. After Briscoe jokes with him, though, he recovers. They go to see Edward about the bearded man.

Edward says that he doesn't remember the man; eventually he admits there was one, but says that it was just a beggar. At the precinct, Briscoe learns that Florence's sister in law didn't know about a new guy either. Logan brings out Florence's datebook for the day in which the man showed up; there's no mention of a suitor. Logan brings out a photo negative, which oddly shows the bomb spring somewhere that it wasn't.

A technician reports that the spring in the bomb is radioactive. It was placed near the film and imprinted upon the film before pictures were taken. The technician eventually explains that the spring is regular steel, but was bombarded with high-energy particles at some point. The only thing that would do that would be close proximity to a nuclear reactor.

->"You got any suspects with nuclear reactors in their basements?"\\
"As a matter of fact, we do."\\
--Technician and Lennie Briscoe

The detectives go talk to Edward. They tell him that the bomb components were radioactive, but Edward quickly guesses the bomb was made of steel, then determines that his reactor couldn't have irradiated the bomb. He tells them to run a gamma ray spectrum. Briscoe says they'll need more of a scientific backing then that; after some technical talk that the detectives don't understand, Edward says he'll get them a textbook.

Briscoe complains to the technician, who runs the gamma ray analysis. He says that Edward's nuclear reactor couldn't have made the spectrum shown by the bomb, but a particle accelerator at Manhattan U could have.

At the accelerator, the lab manager talks about the machine. She says that the head of the lab, Steadmen, once beat Edward Manning to publishing a theory. Steadmen got the Nobel Prize; Edward hated him. Thus, Edward never went to the accelerator. The detectives ask for a list of people who do have access.

They talk to a graduate student, who says that another student, Barry Ramsey, often works late with the lab tools, even though he's not really working with the accelerator. She doubts he knew Florence, or any other women. Talking to Ramsey, he tells them he works late because he has to finish his thesis that year or he's doomed. The accelerator is a quiet place to work late at night. He says he only uses the tools to fix broken appliances, and demonstrates a remote-controlled toaster. He mentions another night-owl at the accelerator, Max Weiss. Weiss wasn't on the list of students; Ramsey says that Weiss's post-doc ran out but he still hangs around there and works. Briscoe asks if he still shows up.

->"Does he still hang around and play with the atoms?"\\
--Lennie Briscoe

He works alone a lot, and hasn't been around in a few days.

The detectives talk to Max's wife, Alice. She sends them to Max's workplace -- he's a bellhop at a hotel. He's visibly disturbed that the detectives went to his apartment, and insists that he really is a scientist, just one with many mouths to feed. They ask about Florence, and he refuses to answer their questions or stand in front of a line up. The detectives return with Cynthia Thomas, who protests that she can't really remember what the man she saw looked like. After seeing one other bearded man, she identifies Max as the man she saw.

The detectives go to the accelerator. After they threaten to dismantle the whole place, Ramsey points out Weiss's desk and drawer, then opens it with a key instead of letting Briscoe jimmy it. The detectives find wires and plastique, and Weiss is arrested. In interrogation, Logan outlines the evidence against Weiss, who only complains that he can't afford the $20 deductible he needs for a lawyer. Weiss freezes up. Van Buren doubts that Weiss would bomb anyone, as he's so meek. Briscoe points out that all the evidence points to Weiss, and all the motive to Edward. Van Buren says they should try to connect the two; in the meantime, they should arrest Weiss.

In Van Buren's office, Briscoe says that Weiss got his degree at the University where Edward used to teach, Weiss called Edward's office several times, and Weiss recently got $3500 from somewhere, despite seeming to be destitute. They still don't have enough, so they talk to Weiss. He again freezes up, so his lawyer, Shelley Connors, shoos everyone but Edward out of the interrogation room. Later, she finds the police and Kincaid, and they offer manslaughter in the 1st degree if he testifies that Edward Manning hired him. Connors says that they'll accept.

In a jailhouse interrogation, Kincaid says that they have a guaranteed conviction of Weiss based on DNA evidence on the stamp,and Weiss says he never wanted to kill anyone. Weiss says that he turned down a job with Edward to work at Oberlin; Edward didn't fill out the letter of reference and Weiss didn't get the job. Stone is unimpressed by Weiss's plea of poverty. Weiss says that he went to Edward for work, and Edward hired him to kill Florence. Edward knew Weiss had Army training and so was decent with explosives.

Edward and his lawyer, Bill Patton, go to Stone's office. Stone ignores Patton's objections of police intrusion into Edward's life. Patton says that Weiss made up the story to reduce his sentence, and when Kincaid produces the $3500 check, Edward points out that he wouldn't pay a hitman by check. He says that he said he didn't recognize Weiss outside Florence's apartment because he didn't think Weiss killed her and so didn't want to get him involved. He says the money was for research he hired Weiss to do. Later, Schiff tells the attorneys to see if Weiss had an actual motive independent of Edward to blow up Florence's apartment.

Alice tells Kincaid that Weiss did know Florence, and liked her, but not enough to kill her in a lover's quarrel. She doesn't believe Weiss is guilty. She says that Weiss got a brilliant physics idea a few months ago, and applied for a grant, but didn't get it. She says that his failures as a scientist explain his moodiness.

In the office, the attorneys try and fail to understand Weiss's papers. They can't find any indication that Edward hired Weiss, but they do find his rejected grant application. It's on proton decay, Edward's field.

The detectives talk to Professor Samuel Kessler. He tells them that Edward's team never actually saw a proton decay, despite an 8 year, $3 million experiment. Edward found this embarrassing and humiliating, but recently came up with some new idea. Kincaid remembers that Weiss also had a new idea, and determines that Edward may have peer-reviewed Weiss's work.

Kincaid sums it up for Schiff and Stone: Weiss wanted to look at Edward's data to try and prove that protons did decay but weren't detected. If Weiss was right, Edward would look foolish. Edward headed the panel that rejected Weiss's work. Stone figures that Weiss went manic over this. Kincaid says that Edward's new idea seemed to require examining the same data that Weiss wanted to review. Edward stole Weiss's idea. Furthermore, Weiss may not have known about the separation, and may have been trying to kill Edward with the bomb.

The lawyers interrogate Weiss again, using a directory they found in his apartment to show that Weiss had the wrong address. Connors shuts down the interview, and says that she wants to get the identification and subsequent evidence thrown out.

Judge Grace Larkin is shown a picture of Weiss in his bellhop uniform, which looks ostentatious,

->"My client was dressed like an organ grinder's monkey."\\
--Shelley Connors

and then makes Stone admit that Thomas only saw one other bearded man before identifying Weiss. The identification is excluded, but the bomb material is in based on inevitable discovery.

Stone and Kincaid go talk to Edward, and tell him they can no longer link Weiss and Florence. Stone tells Edward that they need to supply a motive, and says they know about the theft. Edward says that he began his career brightly, but had petered out. He wanted to contribute something else to the field before retiring and dying. He refuses to testify, even when Stone tells him that Weiss will go free.

->"One single human life on the timescale of the universe... you and I have different priorities."\\
--Edward Manning

Kincaid says that Edward refused to talk even when threatened with subpoenas and contempt citations. Stone decided to attack Edward's scientific reputation. Stone calls Patton and Edward to his office and says that he'll indict Edward for larceny; 4th degree larceny can include theft of scientific ideas. Edward says that larceny implies that the stolen idea had value; he says Weiss's idea had no scientific merit, thus no value, and thus no larceny. He points out that he's the leading authority in the field; if he says the idea was worthless, he'll have the full weight his authority brings him.

Schiff is unhappy about the latest turn of events.

->"What the Hell's the theory?"\\
"That protons eventually fall apart."\\
"Is this someting I need to be worried about?"\\
--Adam Schiff and Claire Kincaid

Schiff points out that they can't prove to a jury that a particle decay theory is good or bad -- juries won't understand any of it. Stone says he'll get other physics professors to testify, but Schiff says the jury will fall asleep. Kincaid recommends using Weiss; after all, it was his theory.

Connors thinks it's ridiculous, but Stone points out that Weiss is doomed anyway. Stone says they're offering Weiss a chance to make his reputation -- they can let him testify under oath that Edward Manning stole his brilliant idea about proton decay. Kincaid needles him by listing all the insults Edward heaped upon Weiss's theory, until they get Weiss to explain it. He does so, concisely and eloquently, and explains that Edward's sensors only looked for one particular sort of proton decay, when other types were theoretically possible.

->"Protons could have been decaying every day!"\\
--Max Weiss

Edward and Stone argue about Weiss's testimony, and Stone lists other professors they'll fly in from across the country to assert that Weiss's theory has weight. Edward says that Stone will ruin his reputation, and Stone says that Edward did it to himself. Edward crumbles, and later in court, he testifies. He said that Weiss's paper helped him realize what he'd been missing, but would have seen it himself soon. He admits to rejecting the proposal due to errors, then shut down Weiss's threats of going to an ethics committee. He offered to put Weiss's name on his paper, but admits he didn't plan to do that, and later told Weiss so. He also admits to paying him a little money to tide him over. When Stone belabors the points that Weiss would receive no credit, Edward says he didn't think Weiss had earned any. When Weiss again threatened him; Edward made sure Weiss wouldn't get a job at Hudson U, so his complaint would carry no weight. Weiss then called to threaten Edward a third time, this time not just with an ethics complaint. Weiss is found guilty.

At sentencing, Weiss apologizes and wishes he could take back his actions. He says that he would give up science forever if he could take back what he did. The judge says he can't, and sentences him to 25 years to life.

Later, Stone says he feels bad about the case, but Schiff points out that Weiss killed someone, same as any other killer.