When their village is being robbed, the twin brothers Hielke and Sietse discover a criminal gang who are distracting the inhabitants with a double of Patrolman Zwart.

Patrolman Zwart is celebrating his anniversary and takes a week off duty. Meanwhile, a new houseboat arrives in Lenten and the mysterious Robert Hofkamp explores for precious belongings. That night, he and his associates Fredje and Bob steal every valuable that they can find. The next morning, Hielke and Sietse Klinkhamer notice strange behavior on the returned Zwart. Realising it's a disguised Bob (who resembles him perfectly), they only have little time left to stop these crooks from leaving the village forever.—Arjen Rooseboom