Sam searches and takes a breath.

Jake and Charles investigate a dangerous serial killer. Holt continues to spar with his rival, Commissioner Kelly. Terry finds out about whether or not he has passed the lieutenant’s exam.

Desperate circumstances call for desperate measures, as Jake, Holt, Amy, Terry, Rosa, and Charles must ally themselves with old enemies.

As fog begins to cover Seattle, the doctors of Grey Sloan navigate through personal complications. Meredith and Alex attempt to save Gus, while Levi talks some sense into a struggling Nico.

While investigating the deaths of Gulliver and Nancy, the dynamic duo of Seattle's winning dance team, Liv and Ravi go undercover as dance partners to size up the other contestants aka the prime suspects. Meanwhile, Peyton confronts Major after she's told that one of his soldiers was out of line during a routine lice check at the school. Lastly, Clive and Bozzio receive a shocking surprise during Lamaze class.

When a teenager is found dead in the Hudson River, Lt. Benson suspects Rob Miller is behind the mysterious death but can’t prove it. Despite having only circumstantial evidence, ADA Stone takes the case to court before Miller can destroy more lives.

Amy and Dina visit Cloud 9 corporate to fix problems caused by Sandra’s misguided activism. Jonah tries to sabotage an employee meeting. Garrett tries to prove to his co-workers that he’s a good person.

Amy and Jonah find themselves on opposing sides as corporate tries to win over employees by showering them with treats. When the company’s tactics grow more extreme, everyone must band together to save one of their own.

Galecki and Cuoco will lead fans on a trip down memory lane, sharing some of the best-kept backstage secrets and personal memories from the past 12 years. They will reveal their favorite moments playing beloved characters Leonard and Penny, and revisit some of the most memorable stories from “The Big Bang Theory Stage.” In addition, the special will feature a tour of the iconic sets, including Leonard and Sheldon’s apartment. This special farewell will include unforgettable clips and interviews to celebrate this beloved series.

Sheldon and Amy await big news.

Bernadette and Wolowitz leave their kids for the first time; Penny and Leonard try to keep a secret; Sheldon and Amy stick together; and Koothrappali makes a new friend, as the gang travels together into an uncharted future.

Actress Jessica Alba; actress Yara Shahidi; The Head and the Heart performs.