It’s pretty easy to hate David McCallum.

Devastatingly handsome Scottish actor. Broke out in the 1962 film “Billy Budd,” stardom in “The Man From U.N.C.L.E.” Television, film and stage career for 63 years, the last 13 in “NCIS,” as Dr. Donald “Ducky” Mallard.

First married to no less than the actress Jill Ireland. She left him for Charles Bronson. Married to Katherine Carpenter, a former model, for 48 years. Eight grandchildren; seems happy as a clam.

And now, at 82, he has published his first novel, a lark of a crime story involving a New York actor out of his depth. Worse, it’s pretty danged good. (Have I said I don’t like this guy?)

“Once a Crooked Man” is mostly the story of Harry Murphy, a 30-something actor in New York, getting by on commercials (“his voice had the essential ingredients of sounding authoritative and at the same time friendly”) and small parts in film and television.

(Courtesy of David McCallum)

One afternoon, just after auditions for a voice-over bit in a mayonnaise commercial and a part in an off-Broadway play, he needs a quick bathroom break.

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He pops into a none-too-fancy Chinese place, the Fiery Dragon. There’s only one table with customers. Before Harry can reach the facilities, the men at the table tell him to get out. Desperate, Harry steps into the restaurant alley to take care of the business at hand . . . and overhears, through an open window, those lone customers planning an execution.

First, this situation is a good reminder to go before you leave home.

Second, it’s a reminder that, should you overhear mobsters discussing a hit, stay out of it.

These low-level, lowbrow gangsters are the aging Bruschetti brothers, Salvatore, Enzo and Max. The problem is Max. He has free run of the young prostitutes for his still-surging sexual appetite in one of their establishments, but he nearly dropped dead of a heart attack a month ago.

As the novel opens, he’s persuading his brothers to cash out of the drug trade, with only a couple of executions needed to secure their safe retirement package.

Cue Harry. Or, more particularly, Harry’s conscience.

Flush with that big mayo contract money (he got the gig!) and pinged by guilt about knowing some poor sap is going to get whacked, he jets off to London to give the elderly target a heads-up. Good deed done, he’ll pop around London and then bounce back to Gotham and his busy, if fledgling, career.

“Once a Crooked Man” tracks how this all goes delightfully wrong, from the hitmen and prostitutes in the Bruschettis’ stable, to their overlords in South American drug compounds, to the sexual concerns of money launderers in the United Kingdom.

It’s all cheerfully implausible in the manner that, say, “NCIS” is implausible but still fun to watch. The only thing that stopped me was a rape-and-bondage scene in which the female victim decides that she likes it so much that she might just drop everything and take up with her assailant. That seemed sort of heavy for a crime caper told in such an otherwise breezy, engaging manner.

After all, McCallum isn’t writing a noirish tale of deceit, vengeance and the hard hustle. This is crime as light comedy, with a broad cast of characters, and you’re not supposed to take any of it seriously. There are guns, a fetching detective and bags of money. It’s a three-card monte as to who winds up where with what and whom.

Neely Tucker is a national reporter for The Washington Post and the author, most recently, of “Murder, D.C.”