The gang all travel to Long Island for Robin and Barney's wedding, but the happy couple make a startling discovery about their families en route.
Louis must hire a professional instructor to give the restaurant staff a sexual harassment seminar, and Eddie tries to impress his friends during a sleep over.
After an armed robbery crew invades a downtown auction house, the case quickly turns personal for Hondo when his sister, Winnie, is taken as one of the hostages.
Jake teams up with Holt's husband to figure out why Holt has been acting moody; Charles tries to get a confession out of an elderly suspect.
Joy's younger sister, Jill, comes to visit, Melanie helps Victoria write a children's book and Elka and Mamie Sue welcome British royalty to Cleveland.