Titles can be misleading. If the single word “Mistresses” (7 p.m., and 8 p.m., BBC America) makes you assume a steamy soap opera a la “Sex and the City” and “Desperate Housewives,” you are less than half right.

Meet Katie (Sarah Parish), an attractive 40ish doctor; Trudi (Sharon Small), a frazzled single mother; Siobhan (Orla Brady), a married lawyer trying desperately if passionlessly to get pregnant; and Jessica (Shelley Conn), a journalist of great appetites who has foresworn marriage and romance.

Within moments of gathering for a birthday party, Katie receives a page and must leave. We know (from the title alone) that she’s not really off to the hospital to save lives, and we soon see her enter a car and snuggle up to a man to whom she is not married.

But in the kind of dark twist that defines this compelling series, we discover that her lover is her patient, a terminal patient at that. And before we can exhale, we’re at his memorial service, attended by the grieving wife and son he left behind.

Sex on “Mistresses” is not consequence-free. We also soon learn that Trudi’s husband died on 9/11.

If Katie and Trudi seem shrouded by mortality, Siobhan is surrounded by a baby-obsessed husband who treats intimacy like a science project and a younger co-worker who walks that fine line between flirtation and harassment. Confirmed in her romantic agnosticism, Jessica is assigned (by her boss and lover) to cover and organize a lavish wedding, where she must confront and choreograph all of the grand romantic gestures she abhors.

The presence of death and the prospect of ruin add a dark edge to “Mistresses” that elevates it above popular soaps of the shopping, shoes and sex variety. There’s more desperation in one glance from Trudi than in five seasons of “Desperate Housewives.” Viewers tired of the trite and untrue should not miss “Mistresses.”

• The White Stripes appear on the final installment of “Late Night with Conan O’Brien” (11:35 p.m., NBC). Conan will become the host of the “Tonight Show” on June 1, after Jay Leno airs his final show May 29. And, as announced just months ago, Leno will host a comedy talk show on NBC every weeknight at 9 p.m. starting later this year. Jimmy Fallon of “SNL” will take over O’Brien’s spot on “Late Night” on March 2.

It remains to be seen whether O’Brien’s obvious smarts and his shelf full of Emmys can equal that intangible quality: cultural resonance. We’re told that late night comics were a central part of last year’s electoral commentary. But while I can recall many moments defined by David Letterman and John Stewart, I don’t remember a single politically trenchant gag from O’Brien or Leno or a single news story arising from their interviews or commentary.

Tonight’s other highlights

• A town full of secrets on “Terminator: The Sarah Connor Chronicles” (7 p.m., Fox).

• J.D.’s dad and champion may tarnish his son’s big moment on “Friday Night Lights” (8 p.m., NBC).

• Echo enters the world of hunting on “Dollhouse” (8 p.m., Fox).

• Scheduled on “20/20” (9 p.m., ABC): Bernie Madoff and his world; an update on last weekend’s report on Appalachian poverty.

• Deadlocked on “Battlestar Galactica” (9 p.m., Sci Fi).