That disarming pair, Jane and Dagobert Brown, as Dagobert, under the influence of Phillips Oppenheim, broods over foreign agents, grows a beard, and finally latches on to the murder of a Patrick Blythe in Cornwall. There, tangled up in Great Danes, codes, a foreign exchange financial deal, a film star, an unwed mother and a psychopathic sister, Dagobert insinuates his way to a correct conclusion... The insouciance and impudence as before.