Despite the hint of a stiff-upper-lip kind of reserve, this is astonishingly brutal. And Firth’s performance makes this dark, dark story land.

Firth is terrific in an unbelievable-but-true tale that charts a course from the ridiculous to the profound.

Directed with even-keeled intelligence by James Marsh, and buoyed by a performance of customary reserve and resolve from Colin Firth, The Mercy tells its story...about as well as it can be told. Yet there’s no denying it’s a muted, disconsolate affair, one that by necessity shrinks before viewers’ eyes into something less rousing and noble than what they were initially promised.

The later stretches, which are forced to become oblique and symbolic in the absence of any hard evidence about what really happened to the sailor, showcase some of Firth’s best screen work.

This unresolved maritime mystery feels oddly flat and functional, diluting a tragic tale full of unanswered questions into an anodyne middlebrow weepie.