You have to be willing to suspend disbelief whenever you watch films like THE SAINT'S DOUBLE TROUBLE, in which GEORGE SANDERS (as "The Saint") discovers that the police are really looking for his exact double who's been committing a number of crimes involving diamond smuggling and a mummy from Egypt. To make sure that audiences know which man we're watching, they have "The Saint" whistling his famous tune as a sort of identification bracelet...but unless you're a fan of the series, you may be missing the clue.
JONATHAN HALE is a nice addition to the cast as Inspector Fernack who, for awhile, is just as confused as everyone else as to the identity of the real criminal. HELENE WHITNEY makes a bland leading lady as the blonde damsel in distress and BELA LUGOSI has a nothing role as a man called The Partner, a colorless part that could have been filled by any nondescript actor in search of work.
There are plenty of escapes for Sanders who is seen narrowly drowning when tied up in a motorboat, leaping onto the back of moving autos to keep track of the kidnapped heroine and making various narrow escapes from the law by devious means. It's his third time as Simon and he looks comfortable enough in the double role, although all the plot twists and turns are a bit hard to swallow with the police and the criminals being unbelievably dumb.
Summing up: Despite obvious drawbacks, it's a fun caper to watch and moves briskly toward a satisfying ending if you're a fan of the series.