Horatio wants to keep the investigation going, but Stetler tells him he’s done.

With Horatio present, Stetler grills Ryan, asking about his gambling debts and pointing out that he was the one who discovered the diamonds missing.

Ryan swears they aren’t his, but Stetler has him taken back to the precinct. Ryan returns home to find his colleagues combing his house for clues, and to see Delko discover the diamonds hidden away in an electronic device. He and Calleigh activate it and drive to the location the car came from and are shocked to find it’s Ryan’s house. Delko assembles a GPS and activates the chip, hoping to use it to backtrack to the bomber’s house. Loman performs the autopsy on Rebecca and recovers a GPS chip from her body which came from the car with the bomb. Ryan questions the man, pointing out that Rebecca Nevins was the one who worked out his plea bargain-which still sent him to jail for ten years. The bomb’s make up matches one from a bomb made in 1999 by a Drew Pollack. Ryan finds the remains of the detonator: a cell phone. Walter and Ryan go over debris from the explosion, discovering hundreds of metal sprockets from golf carts among the wreckage. The inmate is amused to find someone is playing the officers. Horatio and Delko query an inmate, Tino Garvez and learn that Garvez killed Carmichael in 2008. Delko notices that this car isn’t the first Carmichael has signed out. Delko and Tripp question the officer at the impound lot, who shows them the car was signed out to a Detective Stephen Carmichael several months ago. The two CSIs are surprised to find the car came from a police impound lot. Delko helps Jesse get a VIN number off the car next to Rebecca’s that contained the bomb. Back at the scene, Calleigh and Walter are surprised to learn that Delko was wearing a wire at the lab-and that Natalia knew about it. Horatio visits Sully and the retired officer swears that he didn’t discuss Delko’s findings with anyone else. Horatio and the team arrive at the scene, and Delko fills Horatio in on the lead he was pursuing-the theft of the heroin on the 2006 case Horatio’s old partner, Sully, worked. Delko refuses to tell Calleigh why he’s meeting Rebecca, and she starts to leave, but when the bomb goes off, she rushes back to Delko. Rewinding to a few minutes before “Mommie Deadest” ended, “Time Bomb” opens with Calleigh realizing Delko is lying to her and following him to the marina where he’s arranged to meet Rebecca Nevins. They must find the real culprit and exonerate Ryan before things get out of hand. The team is uneasy as Eric returns to do some undercover investigation and evidence leads to the discovery of stolen diamonds in Ryan's house. When Horatio's ex-girlfriend is killed in an explosion, the team looks within their own department to find the killer.

The office season 8 episode 23