Monk is called to a murder at the location where he first heard of his wife’s murder, and while Monk figures out who the assassin is, he doesn’t know that…

A friend of Natalie’s ex-husband seemingly commits suicide aboard a locked cabin on a submarine. Monk agrees to investigate, despite his phobia about being on–and beneath–the water.

McGarrett and Five-0 work with an injured police dog who is the only witness to an ambushed drug bust. Also, McGarrett is visited by Junior Reigns, a former SEAL, who…