Season synopsis
Contains spoilers for this season and earlier seasons.
Russell and Finlay confront crime scenes that appear to have been prepared for forensic investigators, reviving the methods of the Gig Harbor Killer. Jared Briscoe is already imprisoned, but his identical twin Paul Winthrop becomes a suspect in the new murders. The investigation reaches back into their concealed family history, while threats aimed directly at Finlay make the case increasingly dangerous. A staged emergency call and another carefully arranged scene keep the team questioning who is controlling the evidence.
Other investigations continue around that pursuit. Sara and Greg face quarantine after examining a possible infectious threat, and Morgan, Sara and Finlay encounter a shooting at a forensic conference. Nick’s work on the abduction of two teenage girls leads to an offer to run the crime lab in San Diego. He hesitates because his colleagues and years of work have tied him to Las Vegas, even as the opportunity would let him lead a team of his own.
In the finale, Paul adopts his dead brother’s appearance, copying his tattoos and sending Finlay a severed finger among his clues. The pursuit reaches San Diego, where an ambush kills Detective Shaw and Collin Winthrop. Back in Las Vegas, Paul attacks Finlay and locks her in a car trunk. Russell confronts him, and police shoot him when they enter. Paul survives to face prosecution, while Finlay is found alive but remains in a coma. Nick accepts the San Diego post. The season ends at this point; the later reunion film supplies a separate conclusion to the original series.