The funniest part of Cloak and Dagger was watching Gary Cooper (playing an American physicist) try to pass himself off as a German physicist who is visiting an Italian physicist being kept under close observation by the Italian authorities. Mostly because, even though Cooper speaks German reasonably well, he still has his particular drawl, which I'd think would sound rather odd.
The film is not a comedy. Cooper is meant to be helping the U.S. to figure out how far along the Germans might be in their own a-bomb research. A German scientist had fled to Switzerland, and Cooper goes to see her. But his attempts to avoid detection entering the country only raised suspicion and the Nazis whisk her out of the hospital to a secluded cabin. A rescue attempt by Cooper and some local resistance members only succeeds in getting the scientist killed.
Rather than recognize sending a scientist completely untrained in espionage on such a mission was a poor idea, they send him to Italy to rescue the aforementioned Dr. Polda. Who can't flee because the Germans are holding his daughter hostage. So Cooper has to hide out for a week until the resistance can rescue her, before helping the doctor escape. Which gives Cooper time to grow close to a member of the resistance, Gina, as she tries to keep him hidden from the authorities.
Cooper's mistake when entering Switzerland was trying to cleverly hide his face from some German intelligence guy taking snapshots of everyone coming through customs. Now he's in Italy, supposedly on official business, and he's making it impossible to find him. Which surely doesn't raise any red flags. The explanation is his papers won't hold up once they start making phone calls, but he could potentially brazen that out, if he got huffy enough. Play up the wounded Prussian dignity or something. That he's such a big wheel and yet is seemingly going out of his way to stay in meager surroundings and constantly moving only has to make things more suspicious.
There are some good scenes between Cooper and Lilli Palmer, who plays Gina, dealing with basically what Gina's contorted herself into to fight this war. The roles she's played, parts of herself she's discarded, and the fact she'd very much like to return to the person she was before the war. As long as the war is still going, there isn't much chance of that, and she doesn't seem willing to buy into hope that maybe the war could end and let her go back.