- The Control Voice: We all struggle to define ourselves, to live our lives with some sense of balance, with one foot in the past, and the other reaching... for an uncertain future.
An FBI agent (Michelle Forbes) investigates a series of murders committed over the course of 40 years with the same gun.
- The Control Voice: Our yesterdays are like a string of pearls — unbroken — unchanging. But if we could change our past, would that also change who we are?
A Trope in Time:
- Alternate Timeline: Numerous alternate timelines are created due to time travel.
- Asshole Victim: The men killed by the time traveler Dr. Theresa Givens are the epitome of this trope. All 20 of them were future rapists and serial killers whom she killed before they had an opportunity to commit their crimes. She saved the lives of 83 women in the process. Dr. Givens considered their deaths to be just and legal executions.
- Deadly Closing Credits: This episode ends like this, with a newly-forged time-traveling Knight Templar gunning down a serial-killer-to-be who would murder her friend in the future.
- I Hate Past Me: Thoroughly and completed. After saving her 15-year-old self from the rapist who kidnapped her, Dr. Theresa Givens is delighted at having spared that version of herself the trauma that she experienced, allowing her to lead the normal life that she was denied.
- Knight Templar: This episode is a meditation on how Knights Templar come to be created and the price a person pays for being one. It's generally regarded as one of the best episodes of the series.
- Precrime Arrest: Dr. Givens invents a time travel machine after previously having been raped when she was younger. She tried to correct the past by going back in time and killing soon-to-be serial killers before they could claim any victims. She eventually undoes her own motivation to do this by saving her younger self, but previous iterations of events lead a homicide detective to continue where she left off.
- Rape Leads to Insanity: Dr. Givens is raped/assaulted as a teen and grows up to be a mentally-unbalanced scientist who builds a time machine and uses it to go back and execute serial killers before they target anyone. Her ensuing Ripple-Proof Memory does not help with her ongoing mental stability. This is ultimately resolved when a cop goes back in time and saves her from getting raped in the first place. Her altered present self is significantly better off as a result. Sadly, the cop takes her place as the vigilante when her friend is murdered.
- Ripple Effect-Proof Memory: According to Dr. Theresa Givens, this is what happens to whoever uses her time machine to change history.
- Serial-Killer Killer: Dr. Givens uses her time machine to go back and execute famous serial killers before they hurt anybody. Her resulting Ripple Effect-Proof Memory does not improve her mental state...
- Temporal Sickness: It is caused not by the act of time travel itself but by the alteration of history. Whenever an alternate timeline is created, the time traveler remembers both the previous timeline and the new one. Traveling through time and killing 20 future serial killers, creating an alternate timeline on each occasion, takes a serious toll on Dr. Theresa Givens' health and she has a cerebral hemorrhage. Although it is not fatal, she realizes that she does not have long left.
- Time Is Dangerous: The result of Ripple Effect-Proof Memory is that an entirely new lifetime's worth of memories gets added onto the existing one, which could result in brain damage.
- Time-Travel Episode