The death of a young botanist leads the team into the lucrative world of medical marijuana, while Cho’s work with the rapid response team brings him back into contact with Summer.

In the aftermath of the deadly Cylon ambush, Coker threatens Becca, forcing Adama to a heated standoff.

Olivia encounters a very intuitive and oracle-like person named Simone as she looks to recover a key piece of equipment for Walter. Meanwhile, Peter finds himself in a perilous situation as he observes Windmark.

Becca discovers a startling new development that will affect the future of the human race. Meanwhile, Coker’s life hangs in the balance as the team holds out hope for a rescue, and Adama has a disheartening realization about the war effort and his place in it.

Sherlock uses his trademark deductive reasoning skills to find the killer of a college professor, Watson gets a call from a former lover who needs her help.

A national tragedy forces Olivia to return to work at the White House. Meanwhile, we learn more about the first few days of Fitz’s presidency.

A national tragedy forces Olivia to return to work at the White House. Meanwhile, we learn more about the first few days of Fitz’s presidency.

Mike helps his brother Rusty move some furniture into the Heck family’s garage, only to realize the furniture is stolen; Frankie hopes to land a part-time job in a department store so she can get a discount on Christmas presents.

As Oliver and Helena grow closer, Oliver trains her to be his ally, complete with showing her how to use a crossbow. Diggle disapproves of Oliver sharing his secret with Helena as he’s not sure she can be trusted, but Oliver refuses to listen to his concerns. Helena’s quest for revenge proves to be too strong for Oliver to handle after she kills the head of the Triad and all hell breaks loose.

When a bearded, rotund man in a red Santa suit with an ID reading Kris Kringle falls from the sky in Central Park, Castle and Beckett are on the hunt to find the person who killed Santa. But everything isn’t holiday cheer, as they discover St. Nick may have been more naughty than nice. Meanwhile, Castle and Beckett prepare for their first Christmas together.