Ex Post Facto

Kim returns to the U.S.S. Voyager from the Banean homeworld with shocking news: Paris has been found guilty of murder. As his punishment, he's been sentenced to relive the crime from his victim's perspective every 14 hours, thanks to memory engrams implanted in his brain by a Banean doctor. Kim recounts how he and Paris were introduced to an engineering physicist named Tolen Ren, who they hoped could help them repair a damaged piece of equipment. Paris took an immediate interest in Ren's young, attractive wife Lidell, and when Ren turned up dead, he was arrested.

When Janeway orders Voyager to the Banean planet, Neelix warns her that they are likely to be approached by a Numiri patrol vessel, since the Numiri are at war with the Banea. They are stopped by the Numiri, who offer a warning and then allow the ship to proceed. Janeway meets with the Banean Minister, who explains that the evidence — the murder as seen through Ren's own eyes — undeniably proves Paris's guilt. Paris vehemently denies any wrongdoing. As Janeway and Tuvok talk to him, he enters another cycle and once again relives the murder, this time losing consciousness. The Baneans grant Janeway permission to take Paris back to Sickbay for a medical evaluation.

The Doctor reports that the neurological implant is causing serious brain damage. While Paris remains unconscious, Tuvok launches his own murder investigation. He interviews Ren's wife, who says she saw Paris kill her husband. Later, Paris tells Tuvok that he thinks she spiked his cup of tea the night of the murder. The conversation is interrupted by a Numiri attack that the Voyager crew successfully fends off. Tuvok performs a Vulcan mind meld with Paris and relives the 14-hour cycle. When he emerges from the experience, Tuvok declares that he is convinced of Paris's innocence. What's more, he knows why the Numiri chose to attack Voyager.

Eager to clear Paris, and wondering why the Numiri would assault Voyager, Tuvok gathers the key players in the murder mystery. He deduces that a Banean traitor altered Ren's memory engrams, since Paris' daily flashbacks include equations taken from Ren's weapons research. Thus, Numiri agents used Ren's brain to send secret data to the enemy. Having relived the crime from the victim's viewpoint, Tuvok also realizes that the real killer was shorter than Paris, and exposes the Banean doctor who implanted the engrams as both Lidell's secret lover and Ren's killer. A grateful Paris later thanks Tuvok for saving his life.