Milquetoast Edward Everett Horton is the clerical private secretary, in London for some reason, calling upon wastrel Barry McKay, who is being pursued by creditors. McKay comes up with the idea of having Horton take his place -- without telling him, of course -- and assuming Horton's, until McKay's enormously wealthy uncle arrives from London. Complications ensue, including McKay falling in love with his quondam employer's daughter, and the dotty old lady who loved Horton's uncle until he died a quarter of a century earlier, and for whom Horton is named; Alistair Sim is the medium who promises to open communications with her lost love.
It's played extremely broadly. If there are a few scenes intended to open it up from the original stage play by Charles Hawtrey, they are obvious interruptions to the play. Oscar Ashe is amusing as McKay's uncle, who is appalled by Horton, and who thinks there's nothing better than a red-blooded nephew who owes large sums. There are a few funny lines scattered through the dialogue, but the coy score doesn't help much.