A German spy who is sent to Ireland during World War II. The German is instructed to meet an Irish spy named Murphy and confirm Murphy's identity by saying, "The weather could change by Tuesday."
After the German parachutes into Ireland, he sets off for town. Along the way, he asks a farmer where he might find a man named Murphy.
"Well, sir, it all depends on which Murphy," says the farmer. "We have Murphy the doctor, Murphy the postal carrier, Murphy the stone mason and Murphy the teacher. As a matter of fact, I, too, am Murphy, Murphy the farmer."
The German gets an idea.
"The weather could change by Tuesday," he says.
"Aye," says the farmer, "you'll be wanting Murphy the spy."