Scandals in Palm Beach, Fla., are as much a part of the landscape as Lilly Pulitzer and plastic surgery. In recent years, the wealthy enclave has been rocked by the Bernard L. Madoff Ponzi scheme and the Jeffrey Epstein underage-sex lawsuit, to name just two.

Now you can add a bizarre litigation involving Isaac Perlmutter, the enigmatic billionaire chief executive of the Marvel Entertainment unit of the Walt Disney Company.

Befitting a Palm Beach imbroglio, the dispute began over a local tennis pro. Now, at least three lawsuits later, a neighbor of Mr. Perlmutter has accused him and his wife of sending slanderous letters, unsigned, that say the neighbor “sexually assaulted” an 11-year-old “at knife-point” and murdered a local couple.

The hate-mail campaign, which included more than a thousand letters sent to the neighbor’s friends and business associates, is said to be part of an effort by Mr. Perlmutter to pressure the neighbor, Harold Peerenboom, to leave the gated community where they both own homes. One of the letters started, “Today I write you to warn you about Harold Peerenboom of 8 Sloans Curve Road who is a sexual predator.”