Jessica Biel was cast in the New Girl season 4 premiere as Jess' nemesis. Credit: David Livingston/Getty Images

Mary Camden vs. Jess Day? That’ll be a showdown! TV veteran Jessica Biel is returning to small screens everywhere this fall in the season 4 premiere of Fox’s New Girl, Us Weekly confirms. The 7th Heaven alum, 32, will be playing Kat, “the hottest scientist in the world who ends up competing with Jess over a cute guy.” 

The episode, which will air on Sept. 16, features Jess (Zooey Deschanel) and co. challenging each other at a wedding to see who can get lucky. Jess and Kat run into trouble when they find themselves eyeing the same guy. 

Biel spent 10 years on the hit show 7th Heaven as older sister Mary Camden, but since she exited the sitcom in 2006, the actress has stuck to films like 2006’s The Illusionist, 2007’s I Now Pronounce You Chuck & Larry, and 2010’s Valentine’s Day

Justin Timberlake’s wife is next set to star in the romantic comedy Nailed with Jake Gyllenhaal and James Marsden that hits theaters later this year.