Two years have passed since Jack Argyle, convicted of murdering his mother, died in prison — died bearing the stigma of the most terrible crime imaginable. And no one listened to his words that he was innocent. But suddenly the situation changes — Dr. Calgary, a polar explorer, returns from an Antarctic expedition. He knows for certain that Jack had an alibi, and he is determined to find the real murderer and exonerate the convicted man, even posthumously. The Argyle family is unhappy with this turn of events: it now turns out that the killer is one of them, seemingly perfectly respectable citizens...