Sam Spade wasn't available. San Francisco private eye Jack Immendorf was. He was on the trail of the black bird. The Falcon. The Maltese Falcon. "The, uh, stuff that dreams are made of," as Sam Spade liked to say. The bird had flown again, mysteriously taken from its perch in John's Grill.

"Whoever took the falcon knew exactly what they were doing," Mr Immendorf said. "Someone wanted that bird bad."

Back in 1930, Sam Spade, private eye, sat in John's Grill, chewing on chops, potatoes and sliced tomatoes as he worked the case of the missing bird. Dashiell Hammett, Spade's creator, also sat in the joint. Now the 100-year-old restaurant has a second-floor museum dedicated to the writer.

The prize exhibit, among the books signed by Hammett, was the Falcon. Not the original falcon. That one was made of lead. Humphrey Bogart dropped it on his foot and limped through the film. The props department made a couple of plaster replicas of the black bird. One sits in the Library of Congress; the other was at John's Grill, until the weekend.

"I look at it like a Picasso painting," John Konstin, owner of the Grill, told the Los Angeles Times. "The statue had historical significance ... People came from all over the world to see that bird. And we want it back." He has offered $25,000 (£12,600) for its return, "No questions asked." The cops have a lead, but are playing it tight, waiting for the culprit to make a move.

Spade would have enjoyed the story. As he said when he first heard of the bird: "I don't mind a reasonable amount of trouble."