Sister Act: Back in the Habit, Blues Brothers 2000, Look Who's Talking Now, Son of the Mask, Son of the Pink Panther – it seems that the only thing harder to do than comedy is a comedy sequel.

Indeed, The Hangover Part III aims for bluster, dark jokes, shock value and even pathos. But despite its ambitions and lavish production values, it mostly reminded this reviewer of City Slickers 2: TheLegend of Curley's Gold , a tired cash-in that also revolved around a treasure hunt.

To its credit, The Hangover Part III avoids yet another stag party-spiking storyline. It opens with the wild and amoral Mr Chow (Ken Jeong, in full throttle) escaping a Thai prison. We're then reacquainted with the Wolfpack: arrogant, swaggering Phil (Bradley Cooper, coasting), nervous dentist Stu (Ed Helms), perpetual bit-player Doug (Justin Bartha) and unhinged man-child Alan (Zach Galifianakis).

This time the unifying event is the decision to commit the increasingly wild and dependent Alan to an institution. The trip to New Horizons is interrupted by a disgruntled gangster named Marshall (John Goodman), who kidnaps Doug and blackmails the friends into finding their old frenemy, Mr Chow. It seems Mr Chow, now a fugitive, has stolen some gold bullion from Marshall. A disorganised, decadent caper ensues.

Four years ago, The Hangover created at least two stars in the very different shapes of Bradley Cooper and Zach Galifianakis. Here the latter has been uncomfortably shoved into centre stage. Like an especially spicy seasoning, Galifianakis is effective in small doses and hard to take as a main course: it's a fine line between spirited and shrill. Jeong fares better, but talented straight-men Cooper and Helms have even less to do than usual.

The Hangover Part III was always going to be a tough task.There are some bright moments, most of them in the first act and all of which feature in the trailer: a slapstick prison break, an awkwardly funny eulogy, and a perilous situation that becomes a photo opportunity.

Sadly, despite a mostly game cast and handful of chuckles, the film manages to be both bombastic and flat. This hangover offers little beyond headaches, fatigue and regret.