Meredith and Cristina rely on each other as they face more responsibilities at their respective hospitals and cope with life after the plane crash; Cristina helps Dr. Thomas with a challenging heart surgery.
Jack Bauer (Kiefer Sutherland) and his team of agents uncover a plot to assassinate a presidential candidate.
On the hunt for a missing Jack Russell terrier, Veronica comes across a much bigger mystery affecting pets all over Neptune. Weevil is arrested for breaking and entering, as tensions rise in the Echolls family.
A bomb kills five people at a protest rally, and Beckett and Castle try to solve the case by reconstructing the 47 seconds before the explosion.
Jack tries to determine why an airliner exploded over the Mojave Desert, while he continues searching for the assassin who made an attempt on Sen. Palmer's life.
