The CSIs' investigation of the victim of an apparent hit and run leads them into the world of aeronautics.

Back in the States, Carrie and Saul investigate what she saw in Islamabad.

Bo and Tamsin protect a Japanese warrior with a hit on his head. Lauren deals with death threats of her own.

The disappearance of Whitney spurs Helen to scrutinize Noah and his relationship with Alison and her family. Cole searches for answers at Lockhart Ranch. Meanwhile, Detective Jeffries makes significant progress on his case.

When the Serpent Brotherhood wants to kill Santa, the Librarians must rescue him and help him accomplish the true, secret purpose of Christmas.

The team investigates a murder linked to a counterfeit diamond operation, but an illness forces Jane to direct his colleagues from the office as he recuperates. Meanwhile, Abbott is concerned that transgressions in his past could harm his wife’s chance to obtain a prestigious job in Washington, D.C.