Blair Underwood is joining the cast of ABC's "Dirty Sexy Money," playing a thorn in the side of the family with all that dirty, sexy money.

The actor, who also has several other projects in the works, will play a "zillionaire" named Simon Elder on the show, which is scheduled to air on Wednesday nights in the fall. As described by series creator Craig Wright, Elder is the world's third-richest man, thanks to his invention of a superfast computer processor, but couldn't be more different from the old-money Darling family headed by Donald Sutherland.

"Opposed to the Darlings, who live their lives so conspicuously, Simon is always radically underdressed. He lives very simply in a mostly empty loft, and he's sharp," Wright said last week at the Television Critics Association press tour. "He is engaged in a continuous war with the Darlings for the ownership of the island of Manhattan."

Wright also noted that while Elder isn't necessarily a bad person, his vast wealth has had the same corrupting influence on him as the Darlings' money has had on them.

Underwood will be a busy man in the coming TV season. In addition to "Dirty Sexy Money," he also stars in HBO's drama "In Treatment," which is due early next year, and is set to reprise his role on CBS' "The New Adventures of Old Christine." He's also producing shows for TLC and TV One and is finishing up his debut as a feature-film director, the indie drama "The Bridge to Nowhere."

"Dirty Sexy Money" stars Peter Krause as the lawyer for the fabulously wealthy Darling family. The show also stars Sutherland, Jill Clayburgh, William Baldwin, Natalie Zea, Zoe McLellan, Glenn Fitzgerald, Samaire Armstrong and Seth Gabel.