The promise of fun turns into one misadventure after another for the next generation of Griswolds and anyone who encounters them as they head for Walley World.
There's so much dead air in the film that I wondered whether punchlines had been cleaved out to secure a PG-13 rating, but no: it's a hard, inexplicable R.
The writers have decided that the more dirty words you stuff in an 8-year-old's mouth, the funnier he becomes. Even before the family leaves Chicago, the audience longs for them to visit a bar-soap factory and feed Junior a few samples.
Wacky hijinks ensue, some of them very funny, some dipping desperately into bad taste, some just falling flat. (Which, it's worth remembering, was the case with even the best films of this franchise.)
It holds on to the original's acrid cynicism for the first 40 minutes or so before turning predictable and bland. There are some real, nasty laughs to be had here, but they're front-loaded.
Ultimately "Vacation" 2015 is an unknowing spoof, aping a series of - rightfully or not - beloved films without understanding at all what made them tick.
