When Columbo plays darts in the Irish pub, his first shot hits above the number 20. When he takes his second shot, the first dart now appears below the number 20. On his third shot, the first dart is in its original position above the number 20.
The orientation of the writing and dedication in the book changes between shots.
When at the hotel room, Columbo's cigar disappears from his hand while he takes out the sliding drawers from the suitcase that contain the guns. After he places the drawer back into the suitcase, his cigar reappears in his left hand.
After Devlin shoots his round of darts, he goes to remove them from the board, and they are completely different from what he had shot beforehand.
In Mr. Pauley's hotel room, a bandage on Columbo's left pinky appears and disappears between shots.
Devlin collected all the papers in the hotel room but failed to check the arms dealer's coat's pockets; and if he did, failed to check the book for anything stuck in between pages. He should have taken the book with him to remove all possible links between him and the dealer.
However, after his first encounter with Columbo, Devlin admits this mistake to himself, saying "You bloody fool!" to his reflection in a pinball machine.
At the dock when Columbo gets a flat, he asks Devlin for a dime. When the tow truck picks him up and he hears Devlin on the radio, though, he stops to use a payphone and has change to call the station.
However, one should remember that Columbo always misplaces everything and that he finds what he needs when the need arises.
However, one should remember that Columbo always misplaces everything and that he finds what he needs when the need arises.
Devlin speaks of a famous Irish philosopher named Georg Wilhelm Friedrich Hegel. Hegel was, in fact, German. But most likely, Devlin was joking about Hegel being Irish.
When Columbo goes to the pier to harass Joe Devlin, he gets a flat tire. The flat is on the right front side. Columbo's spare tire is at home, so he borrows a dime to get the car towed, but when the Peugeot is being towed, the tire appears to be as good as new. Why would he need a tow when the tire is fixed? When the weight of the car is lifted off of the tire, it no longer appears flat.
When Devlin is in the RV, all the guns are neat rectangular box-like. But when unwrapped, there's no box. Just the gun. There's no way all the packages could be those neat boxes with sharp angles.
Devlin declares that he is "a boy from the backstreets of Belfast", but his accent is a Southern Irish one, quite unlike that of Belfast in Northern Ireland. Also, when playing darts, he refers to a pub in "Londonderry". A genuine Irish Republican would never refer to the city by that name, and would call it "Derry".
When Columbo is in Pauley's hotel room trying to figure out how the whiskey bottle ended up right next to the body, Devlin turns up out of the blue. This would give away the fact that he knew where Pauley's hotel room was and prove his guilt, yet Columbo never picked up on it.
Devlin touches both the whiskey bottle and the glass in Mr. Pauley's room, yet the police don't check them for fingerprints. As Devlin previously was in jail in England, his prints would be on record. Even if those records weren't available for some reason, Columbo is wily enough to get Devlin's prints on some pretext or another.
Columbo asks to borrow a dime from Devlin to call the tow truck; however, while riding in the tow truck, he asks the driver to pull over so he can make a call, at which point he pulls out a dime.
Joe Devlin originally agrees to purchase 500 M-11s for $300 per unit. However, when the deal is delivered in the hotel room, Mr. Pauley agrees to deliver 300 M-11s.