Flick's sausage, containing the forged painting, is kidnapped by the Communist resistance who demand a ransom for its return. Von Strohm and Geering, anxious that Flick does not discover their part in the deception, get Rene to pay the ransom which he does with money Edith obtains from Alphonse. Dressed as a German soldier Rene drops off the money, observed by both German and French parties also in disguise. However Gruber turns up with his dog who runs off with the sausage.
Gruber is about to mince the sausage his dog brought in when he discovers the painting. The Resistance pay off Alphonse,who provided the ransom money,with notes forged by LeClerc whilst Gruber is ordered to fake another copy of the picture. Michelle intends to get the airman out using an old aeroplane in the museum. It will be powered by the motor from Von Klinkerhoffen's lawn mower,which she has smuggled out in Madame Fanny's wheelchair.
Waitress Maria is sent to Gruber with the genuine painting in order for him to copy it. However she is intercepted by Von Klinkerhoffen who puts the painting,inside the sausage,in his wardrobe and refuses to release Maria until he gets his lawn mower motor back. Rene,Von Strohm,Geering and Flick,using the secret passages,break into the chateau to steal back the painting.
Rene has successfully got the painting back so Michelle concentrates on her plan to get the airmen away in the ancient aeroplane. It is to be drawn by a car and catapulted into the air,requiring Rene to steal 800 metres of men's braces,which he does under the guise of his Brotherhood of the Night-Owl. Flick and Helga,aware that something may be afoot,turn up in his staff car but it is flattened by a runaway steam-roller so they miss seeing the failed escape when the plane fails to take off and Rene is flung through the air.
The airmen are disguised as waitresses at the cafe.However,Von Klinkerhoffen recognizes a Van Gogh,behind which Rene has hidden The Fallen Madonna,and he requisitions it to be taken to the chateau,along with the two 'waitresses'. To thwart this an elaborate pantomime is staged,whereby the two men dress as tarts out to seduce Rene.A supposedly enraged Edith then 'shoots' them with a gun loaded with blanks. The 'corpses' are taken to Alphonse's funeral parlour under which a tunnel has been dug,connecting to the prisoner-of-war camp across the road,in which it is planned...
As Rene communicates with London on the radio hidden under Madame Fanny's bed Flick listens in and learns of the plan to dig the tunnel into the prison camp. The airmen and Alphonse need help in digging so Rene and his staff join in. Von Strohm and Geering follow Rene and go through the tunnel,which collapses behind them,trapping them and Rene in the camp with the airmen and the cafe staff. Von Klinkerhoffen is about to make his inspection of the prisoners but the Germans and the girls are disguised as British servicemen and fool him.