In an effort to shore up sagging ratings, “ER” will soon welcome Rebecca DeMornay, Alan Alda and Maura Tierney to the halls of County General Memorial Hospital. Variety reports that DeMornay (“The Hand That Rocks the Cradle”) has signed on to make her first foray into series TV with an initial five-episode story arc. (Alda will also appear in five episodes, while Tierney is in the final stages of negotiations about her guest shot.) Debuting on the “ER” season premiere, DeMornay will play a socialite who becomes romantically entangled with Noah Wyle’s character.

  • “ER” has taken a noticeable ratings hit since George Clooney left last season after fulfilling his five-year commitment to the show. Even so, NBC’s “ER” begins its sixth season in the fall as the most-watched program on TV.