Mr. Wong in Chinatown

A pretty Chinese woman, seeking help from San Francisco detective James Lee Wong, is killed by a poisoned dart in his front hall, having time only to scrawl 'Captain J' on a sheet of paper. She proves to be Princess Lin Hwa, on a secret military mission for Chinese forces fighting the Japanese invasion. Mr. Wong finds two captains with the initial J in the case, neither being quite what he seems; there's fog on the waterfront and someone still has that poison-dart gun...