If you were facing the prospect of rape and worse from a invading Japanese Army then one of the last people you would look to for help would be a mercenary American mortician with a drink problem.
Yet Christian Bale's John Miller, an eye-on-the-main chance Western drifter, becomes an heroic man of the moment when he opportunistically takes the cloth and poses as an American priest in a besieged Catholic church.
It's December 1937 and, after successfully taking Shanghai, the Japanese Imperial Army have ramped up their bestial policy of gang rape and civilian executions to unheard of extremes in the Chinese capital of Nanking.
Stumbling over the corpses of the murdered, Miller picks up two terrified teenage girls who lead him to a Catholic church where the incumbent priest has been killed and a plucky teenage boy (Tianyuan) acts a gatekeeper.
A dozen or so young orphan girls are joined by a garish group of Nanking hookers - led by luminous beauty Mo (Ni Ni) - who force their way in and make themselves comfortably at home in the church cellar.
The money-grabbing Miller, meanwhile, sees the opportunity to plunder church funds and knock back the communion wine...until a terrifying sequence where an out-of-control Jap platoon embarks on a practically unwatchable gang rape of the girls sees him discovering a moral backbone of steel.
Director Zhang Yimou brings his customary visual flair to a story that does not always need it - the ravishing shots of shattered stained glass sometimes sit awkwardly with the the vile human atrocity that is being committed alongside.
Yet is is impossible not to be moved. Bales sometimes overeggs his Western saviour yet is watchable throughout, imbuing Miller with a nobility that is only explained in the final reel.
The overriding atmosphere is one of sheer terror - cue mind-numbing scenes clinically displaying Imperial Army war crimes, particularly one harrowing instance where two courtesans on a foolhardy trip back to the brothel are spotted by a Japanese patrol. Even the Japanese equivalent of the mythical 'Good German' turns out to be a duplicitous swine.
Cynics may find the final plot twist sentimentally convenient (even if it was based on a true story) but there's no getting away from a war crime where the guilty cannot even claim they were obeying orders.