Nominally retired, their sleuthing and treasure-hunting days are behind them. Bélisaire has turned author of thrilling yarns based on their exploits but his wife misses the thrill and is bored. She decides to get back into the game and starts a detective agency with quick results; a celebrity arrives asking her to track down his missing fiancee. The path leads to a secluded health spa where it seems that a cure for ageing may have been found.
This is compounded by a final act twist which feels entirely incongruous introducing a supernatural element entirely at odds with the narrative up to that point. This may well be a recurrent aspect of the Beresford's adventures but here it sees the gum-shoeing sidelined - or in fact, finished early - in favour of a more overtly farcical fare. This means that the film ends on a rather bum note rather than a satisfying conclusion to the case.
Still, as far as frothy French capers go, it does the job required of it and as noted, the two leads are delightful company. What Thomas' Partners in Crime (2012) feels like it needs are a few more laughs, or a more enthralling mystery, to counteract its disappointing finale.