The title and cartoon itself are a parody of a 1950s crime serial called Boston Blackie.
"Friend to those who need no friend, enemy to those who have no enemies", Boston Quackie (played by Daffy Duck) is an American agent enjoying some time in Paris with his girlfriend Mary when his boss Inspector Faraway (played by Porky Pig) comes to him with an assignment. The inspector hands Quackie the briefcase that has to be delivered to the Slobovian consulate - however, secret agents will try to steal the briefcase. Immediately on turning his back and he is given the briefcase, Quackie lost the briefcase by a man wearing a green hat. Quackie, Mary and his boss chased after him. Quackie follows the man to the Cloak & Dagger express train, and tries various ways to prove that the man wears a green hat and thus is the man he's after. With some help from Porky and Mary, Quackie eventually prevails, getting the briefcase to the Slobovian consulate. However, he's dismayed when the consulate pulls out what appears to be a simple bottle (saying "You mean, all that hassle just so you could have a coffee break?"). The consulate pours some water in the bottle, shakes it, and out pops a beautiful woman in an evening dress - the consulate needed a date for the embassy ball. Quackie then looks at the label for the bottle - "Acme House Instant Girl" ("Directions: Add water and pour" being written in another label on the back side of the pot), and admiringly says, "You know, there just might be a market for this!"
The syndicated Merrie Melodies deleted some of the spy murder gags on the train, and briefly cuts the scene when Daffy is "hanging" in the mailbag.
- The 1946 Looney Tunes theme "The Merry Go Round Broke Down" played instead of the 1955 version. This mistake would be made again with The Duxorcist shown as an individual cartoon short.
- Although this is a Looney Tunes short, it has the Merrie Melodies closing card.