Marshall quits his job at Goliath National Bank to volunteer at an environmental organisation; Ted and Zooey continue to butt heads over the future of the Arcadia.
When a police dog handler is murdered, the only living witness is his canine partner. DB Russell and his team try to find the killer; Finlay and Morgan investigate the shooting of a high-profile divorce lawyer.
Hank's dreams are haunted by Carrie; Charlie and Hank meet rocker Atticus Fetch.
Karen asks Hank to intervene with Becca; the boys board Air Force 69 with Atticus Fetch.
Marshall and Stan are forced to deal with a rock star witness, whose identity is compromised, while Mary's road trip is full of revelations.