Frank must race to stop a biological weapon attack on New York City, while keeping it a secret from his family during their most sentimental holiday, Mother’s Day. Meanwhile, a long-standing conflict between Danny and Jamie comes to a head.
After Juliette stumbles upon a brutal murder, Nick learns the suspected creature, and friend of Monroe, is suffering from a mysterious condition — the inability to completely return to human form. This mysterious condition leads them to a therapist who’s created an artificial drug to suppress the creature side, with horrifying side effects. Meanwhile, the investigation takes a surprising turn when Hank sees something he can’t quite explain.
Dave welcomes actor Jon Cryer from the CBS comedy series "Two and a Half Men", comedian Tommy Johnagin and musical guest M.Ward.
Jon's German fans get a surprise when they visit his star on the Walk of Fame.
In order to defeat Dick Roman and the Leviathans, Sam and Dean must locate three key items. Castiel helps with one but for the last objects, the Winchesters must face two of their strongest opponents - an Alpha and Crowley. Meanwhile, Bobby tries out a new ghost trick that ends up being very dangerous.