When Maud Marsh flings herself into George Bevan's cab in Piccadilly, he starts believing in damsels in distress… George traces his mysterious travelling companion to Belpher Castle, home of Lord Marshmoreton, where things become severely muddled. Maud's aunt, Lady Caroline Byng, wants Maud to marry Reggie, her step-son. Maud, meanwhile, is known to be in love with an unknown American she met in Wales. So when George turns up speaking American, a nasty case of mistaken identity breaks out.