DESPERATE HOUSEWIVES - "The Chase" - When Celia comes down with the chicken pox, Gaby must keep her distance, on ABC's "Desperate Housewives," SUNDAY, FEBRUARY 28 (9:00-10:01 p.m., ET). Having never had the chicken pox herself, Gaby stays with Tuc and Bob and is reminded of what it's like to be single again; Lynette and Tom forget Penny's birthday; Bree hires a promising new employee; Susan cheats on Mrs. McKluskey; Katherine makes a surprising discovery; and Angie grows concerned over Danny's disappearance. (ABC/RON TOM) EVA LONGORIA PARKER