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 intial J in the case, neither being quite what he seems; there's fog on the waterfront and someone still has that poison-dart gun...
Boris Karloff
as Mr. James Lee Wong
Marjorie Reynolds
as Roberta 'Bobbie' Logan
Grant Withers
as Police Capt. Bill Street
Huntley Gordon
as Mr. Davidson
George Lynn
as Capt. Guy Jackson
William Royle
as Capt. Jaime
James Flavin
as Police Sgt. Jerry
Lotus Long
as Princess Lin Hwa
Lee Tung Foo
as Willie
Bessie Loo
as Lilly May
Ernie Stanton
as Bailey
I. Stanford Jolley
as Palisser Hotel Clerk
