Reviews don’t often discuss the duration of films and, when they do, it is usually to complain that something is bum-bustingly long.

In contrast, Mathieu Amalric's fourth feature as director – folowing the mildly diverting On Tour – is notable for its extreme brevity. At 76 minutes, The Blue Room is surely the shortest live-action feature released this year and it does feel disappointingly slight.

Indeed, adapted from a novel by Georges Simenon, the piece comes across as the sketch for an uncompleted thriller. It’s a promising sketch. The director is convincingly hounded as a man who may be guilty of something awful. Christophe Beaucarne’s camera enjoys the seedy passion of a snatched love affair. But what’s here is not all that should be here.

The Blue Room begins by cutting from the police's interrogation of Julien (Amalric) to his passionate entanglements with Esther (Stephanie Cleau), a chemist's wife, in the blue room that lends the film its title.

As in the novels of Barbara Vine, the question here is as much “what happened?” as “who did it?” Is that drop of blood on the sheet significant or is it a visual distraction? Who’s persuading whom down what dangerous path?

Amalric’s film is not short on atmosphere. The pounding paranoia is well maintained during the interview. The sensual surge is overpowering in the blue room.

Amalric the actor mashes considerable charm with a ferret-like untrustworthiness into an unstable package that perfectly suits such ambiguous material.

Amalric the director is less effective at fitting Simenon’s antique sensibility to modern France. The technology seems to be contemporary, but the manners feel like those of the immediate post-war era.

Diverting for all that. While it lasts.