While investigating the murder of Greg Franklin, Briscoe and Curtis discover the victim was killed with bullets that had been coated in fulminated mercury. They learn that Franklin had recently been fired from his job at a university and was still receiving mail via his old employer. This leads the detectives to a student named Alan Sawyer. Briscoe and Curtis get enough evidence from a search to arrest Alan, who confesses to the murder. But it becomes apparent that Alan is severely mentally ill. He is diagnosed schizophrenic, and was part of an experimental drug trial led by Dr. Varick, a professor in the university's psychology department. Varick says that Alan's schizophrenia has been in remission ever since the trial began. The defence gets Alan's confession excluded as evidence, and the case is thrown out.
Alan's parents claim that he recently visited them and his illness was clearly worse than ever, but Dr. Varick dismissed their concerns. Skoda and another psychiatric doctor both testify that Alan's health has deteriorated and he is a risk to himself and others. But Varick sticks to the story that the test drug is keeping Alan's symptoms under control. The judge believes him, and won't sign an order to commit Alan to hospital. Ross and McCoy find out that Varick was implicated in the suicide of a subject in a previous drug trial, but was found not guilty. Varick's research assistant, Jill Perry, was responsible for collecting test data and approving all patient reports. It becomes clear that Varick is using her as an accomplice so he can continue to be funded by the drug company.
McCoy and Ross convince Perry that Varick has set her up to take the fall if anything goes wrong with the study. She tells them that when Alan began to relapse, Varick insisted she falsify test records. Even when Perry reported that Alan was hearing voices telling him to kill Franklin, Varick wouldn't listen. A closer look at the research budget leads to the discovery that Varick was supposed to order brain scans on all the patients, but he didn't do this until Alan began to relapse. The scan showed Alan is not schizophrenic but has a brain tumor, which is now inoperable, so Alan is going to die. If Varick had said something, it would have been caught earlier and Alan may have survived. McCoy intends to charge Varick with murder after Alan dies.
This episode contains examples of:
- Downer Ending: Alan has an inoperable brain tumor and only a year or so to live, Franklin is dead, and Perry's research career is ruined even though Varick's the one who bullied her into co-operating.
- Halfway Plot Switch: The first half of the episode is about the investigation into Franklin's murder. The second half is about the investigation into Varick's drug trial.
- Insanity Defense: Alan uses this defense. For a change, the prosecution chooses to accept it.
- Hearing Voices: Alan believes he hears voices of historical figures and they told him to kill Franklin.
- Mighty Whitey and Mellow Yellow: Subverted when Sawyer tells the detectives he's tried to ask out his Vietnamese classmate, but she's more interested in her celebrity crushes.
- The Scrooge: What Ross thinks of McCoy, who insists she cut corners to save money when making copies of evidence. However, the implication is there for Christian Varick, who skipped a critical step prior to the study that Alan was in, and that was for each student to have a brain scan.
- Teacher/Student Romance: Sawyer didn't tell anyone about his involvement in the drug trials, leading one of his classmates to think he was having an affair with a professor in the psychology department which was why he spent so much time there.
