RAY: This next puzzler is from my World War II series. The inspiration for it was sent in by Todd Markin.

TOM: Is there a dimly lit Quonset hut involved?

RAY: You'll see. D-Day is approaching. It's vitally important that the location of German troops and ammunitions dumps be communicated to the Allied Command in England. The French Resistance fighters must now be put to work. Rail lines and bridges need to be taken out, and the timing is critical.

Radio communication is too risky. Information must be exchanged in person. To that end, a small boat leaves England headed for the French coast. Two robust young men quietly work the oars. There's no moon this night, and the thick overcast is an unexpected yet welcome measure of security.

The third man in the boat is too old and feeble to be of much use rowing. He works the signal light as they near the shore. Three quick flashes follow by a pause, and then two flashes. His counterpart, a retired cavalryman, a veteran of the Great War, is hunkered down in the sand on the French coast.

He signals three quick flashes with his light, then the all clear to come ashore. The men quickly exchange documents and in an instant they're gone, the Frenchmen disappearing into the inky shadows. The three men in the boat swiftly and quietly row back to Mother England.

Now, here's the interesting part. The soldiers of the German shore patrol, and there were many of them -- each with the keen eyesight one would expect of young men -- didn't see them or their flashing signal lights.

The question is, why not? I'm going to give you a hint. It had to do with the old men.