Les couples sont de retour pour un mariage à Las Vegas, mais ce qui devait être un week-end romantique vire en cauchemar lorsque leurs diverses mésaventures les amènent dans des situations compromettantes, qui menacent de faire tomber à l'eau le mariage.
Rory MacNeil, a rugged old Scotsman, reluctantly leaves his beloved isolated Hebridean island and travels to San Francisco to seek medical treatment. Moving in with his estranged son, Rory sees his life transformed through a newly found bond with his baby grandson.