Melissa McCarthy's latest comedy is something of a cautionary tale. It tells a story with a profound moral, though not the one its creators intended. The movie's message: America's plus-size sweetheart is in danger of making the Eddie Murphy Mistake.

Some of you will remember that Murphy, now a bitter has-been, was once the biggest entertainer on the planet. He shot to fame with a stint on "Saturday Night Live" and became a bona fide Hollywood star with back-to-back box office smashes — 48 Hrs. (1982) and Trading Places (1983). Then he did something that would ultimately define his professional existence. He made a movie for the money.

It was called Best Defense (1984), and, as the actor himself admitted, it "sucked real bad." Murphy made it anyway, because, as he later explained to David Letterman, "It had a check like I had never seen before. My morals and principles went right out the window. My career almost went out with it, too."

Murphy starred in another credible effort or three but eventually fell into the habit of making films for the money. Thirty years later, that's his legacy. The list of dough-motivated duds such as Harlem Nights (1989), Boomerang (1992), Vampire in Brooklyn (1995), The Adventures of Pluto Nash (2002), Norbit (2007) and Meet Dave (2008) is as long as it is disheartening. A great comic mind is a terrible thing to waste.

Like Murphy, McCarthy made a splash on TV and then skyrocketed to stardom with indelible performances in a pair of hit comedies — 2011's Bridesmaids and, two years later, The Heat. Anyone who reads my reviews knows I love her. Which is why I worry about her making the Eddie Murphy Mistake.

Let's be honest: Identity Thief (2013) and Tammy (2014) may have helped make McCarthy No. 3 on Forbes' list of the world's highest-paid actresses, but they also reflect a downward artistic trajectory. One that, I regret to report, continues with The Boss.

Essentially an extended sketch based on a character McCarthy created when she was a member of the Groundlings comedy group, the film tells the most lightweight and formulaic of stories. McCarthy plays Michelle Darnell, a self-help guru who's amassed a fortune spreading a gospel of self-absorption. In her world, there's no room for nonsense like loyalty, love or family.

Convicted of insider trading, Darnell is sent to a Club Fed facility à la Martha Stewart. With a significant difference: When Darnell gets out, her assets have been seized, and she's forced to bunk with her former assistant, Claire (Kristen Bell), and Claire's adorable daughter, Rachel (Ella Anderson). From this point on, only two things that matter happen.

No. 1: The ex-con hatches a mildly amusing scheme to amass a second fortune by forming a group that's a cross between the Girl Scouts and the Hells Angels to sell Claire's irresistible brownies door-to-door. No. 2: Touched by the way the little girl and her mother welcome her into their lives, Darnell realizes she craves love and family after all. The third act contains more sweetening than the baked goods.

Directed and cowritten by the star's husband, Ben Falcone (Tammy), the movie offers occasional reminders of the actress' prodigious gift for improvisation. But it relies way too heavily on pratfalls, lame gags and profanity for its finite allotment of laughs. More disappointingly, it gives us a McCarthy who, for the first time, appears content to play it safe in exchange for a fat check.

Just ask Murphy. When you make it big, that's the biggest mistake you can make.