There is a striking, butterscotch-gold silk dress that Keira Knightley wears in The Aftermath. Its neck is a halter, the straps making an X at her throat. It dips seductively low in the back; shortly, its front will be speckled with a fine spray of blood.

In the same way that Knightley wore the hell out of the vibrant emerald gown Jacqueline Durran designed for 2007’s Atonement, she makes an impression here in writer-director James Kent’s handsome second feature, set in Hamburg circa 1945, in the aftermath of the Allied victory. It feels wrong to reduce the entirely capable Knightley to her costume, especially given her nimble and lively turns in recent films Colette and the forthcoming Official Secrets, but her performance here is tic-y, affected, prim, only really coming alive in the steamy love scenes with Alexander Skarsgård’s hunky German architect (no grown man has ever looked as good in a cardigan).

Knightley plays grieving mother Rachael, who is struggling to settle into the mansion she and her husband, Captain Lewis Morgan (Jason Clarke), have requisitioned, uncomfortable sharing it with its original German owner, Stefan Lubert (Skarsgård) and his teenage daughter, Freda, (Flora Thiemann). Though its plotting becomes soapy somewhere in the first act, things eventually build to a satisfying emotional finale. Still, something is missing; the tone frustrates, caught awkwardly between lusty, full-out melodrama and thin period drama.