Mr Wong in Chinatown (1939) starring Boris Karloff

A pretty Chinese woman, seeking help from San Francisco detective James Lee Wong (Karloff), 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. Marjorie Reynolds as Roberta 'Bobbie' Logan, Grant Withers as Police Captain Bill Street, Huntley Gordon as Mr. Davidson, George Lynn as Captain Guy Jackson and William Royle as Captain Jaime,