Total of episodes: 160
In the first season, the team is introduced to the viewers, cases are solved and missing people are found
As the team continues to track down missing people, Jack and his wife slide towards divorce, while Jack must also care for his father (Martin Landau) who has Alzheimer's disease. We learn about the team members' life histories, including the fact that Martin was practically raised by his aunt and uncle, and Danny is an orphan whose brother (Alex Fernandez) is a convicted felon. Martin fatally shoots a child sex trafficker, and both he and Vivian must keep quiet in order to keep their jobs. Jack makes a last ditch attempt to save his marriage by moving to Chicago with his family, giving Vivian a long-awaited promotion to his post, but at the last minute his wife leaves without him, taking their daughters with her.
Vivian loses her promotion when Jack returns to his job, causing some commotion among the group. She also experiences heart trouble that endangers her life and her career, and undergoes risky surgery. Martin and Samantha begin a secret office romance, and it ends badly. Jack undergoes a brutal custody battle with his ex-wife. Danny has to confront his traumatic past, and his estranged brother. The season ends with a cliffhanger as a hired mercenary opens fire on Martin and Danny's car while they transport a prisoner. Guest star Bradley Steven Perry .
After barely surviving the gun battle that ended Season Three, Martin must recover from near-fatal gunshot wounds while Danny battles PTSD. Stretched for help, the team gets a new member, Elena Delgado, a former NYPD vice squad officer with an aggressive, streetwise attitude. She has a past connection to Danny, the nature of which is unknown until Season Five. Martin develops an addiction to painkillers, and Jack begins a romance with the widow of a former mentor killed in the line of duty.
Vivian is put in charge of a task force to locate the serial kidnapper, who is part of a sex trafficking ring. Samantha reveals that she is pregnant from a one-night stand with a bartender, Brian; by the end of the season, he waives paternal rights and she gives birth to a son. Jack begins a pattern of roughing up suspects to make them talk, which appears to be related to PTSD. He also gets into a dangerous situation without backup and is nearly killed, and becomes over-involved in the life of a teenager he saved from the sex traffickers. In the season finale he is demoted and put in mandatory therapy with Dr. Clare Bryson (Linda Hunt).
This season also contained a two-part crossover episode with CSI, as Jack and Gil Grissom and their teams track down a serial killer responsible for the disappearance of a boy six years ago. Both episodes are included on the DVD collection for CSI's eighth season.
Without a Trace completed twelve episodes of Season Six before the Writers Guild of America strike. Because the show's writing staff all joined the strike, there were no more new episodes until the issue was settled. Once the strike ended, the show returned April 3, 2008, with six episodes.
The series' seventh season began airing September 23, 2008, on a new 10:00 pm (EST) Tuesday timeslot. Steven Weber joined the cast for the first five episodes of the season as Special Agent Clark Medina, Jack's temporary replacement as unit supervisor. The episodes focused as much on missing persons cases as on Medina's war against Jack, as he revealed that he had not only been sent to replace Jack but also to convince Jack to leave the bureau. Medina ultimately realizes that he cannot get Jack to resign, and uses him in a power play to get himself promoted; in return, he arranges for Jack to get his old position back. Following Jack's return to Unit Supervisor, he sets about trying to repair his relationship with Sam and takes custody of his elder daughter, Hanna. The series ends with Jack putting a permanent end to his and Sam's on-again-off-again relationship and reaching a point of reconciliation with Hanna; Sam and Brian decide to live together to raise their son; and with the team attending the wedding of Danny and Elena.