Gerard Depardieu and Isabelle Huppert have not occupied the same cinema screen since they appeared Maurice Pialat's Loulou 35 years ago. They have grown older in very different ways: Huppert is a more distinguished version of the stern presence she one was; Depardieu has become his own Spitting Image puppet.

How might they work together on screen in their current condition? Brilliantly as it happens. Playing an estranged couple meeting up to fulfil a promise to their late son, the two veterans form a lovely, complementary partnership.

Depardieu seems willing to remove his top and allow the mountainous masses below to act as comic relief at every opportunity. Huppert pinches her face and exercises that guttural rasp with a compelling blend of anger and regret.

What a shame they are not in a better film. Were almost anybody else in Guillaume Nicloux’s sentimental piece it would barely be worth releasing outside France.

Depardieu and Huppert play two actors who, years after their parting, receive letters from a son in San Francisco who appears to have killed himself. The instructions are baffling. They are to drive to a certain point in Death Valley and wait for him to “return” and greet them. Initially, most sensible adults will assume that the late young man was talking metaphorically, but, as they drive deeper into the heat, apparently supernatural occurrences suggest he may have meant the promise literally.

The problem is not that the later developments are implausible (we've bought many ghosts in fiction). It's that they don't fit at all comfortably with what has gone before. To that point, Valley of Love has been a perfectly watchable semi-comedy featuring excellent duologues between untouchable professionals. Then it takes a turn into the barmy world of mind, body and spirit.

Get together again, guys. Pick a more consistent script next time.