When Dr. Müller is delayed and postpones his own wedding his furious bride Inge leaves him and goes to see her aunt, picking up smart Fred on the way who poses as her husband since Inge is too embarrassed to talk about her busted nuptials.
Nathan Flomm, in order to avoid the humiliation of having missed out on a hugely successful business, assumes a new identity on Martha's Vineyard. He plots revenge when his former business partner moves to the same town.
Father-to-be Alan is shocked to learn that he was born a sextuplet. With his newfound brother Russell riding shotgun, the duo sets out on a hilarious journey to reunite with their remaining long-lost siblings.