Compelling portrait develops over season

And that has been one of the many beauties of this Showtime series, which wraps its first season tonight at 10:30. The story began as a black comedy about Falco’s subversive RN manipulating the system at a New York hospital to help those rushed into her ER. We saw Jackie save lives by illegally harvesting organs, and we saw her comfort those treated like robots by clueless doctors.

But “Nurse Jackie’’ evolved into a piercing psychological portrait of a fractured soul whose compassion for her patients never extends to herself. Addicted to painkillers and mired in an adulterous affair, yet quite brave and stoic, Jackie emerged one of TV’s most sympathetic messes.

Those who thought “Nurse Jackie’’ was simply going to be a love song to sensitive nurses were wrong. The show is a much more faceted look at those who practice the art of healing, and it has offered no easy solution to the crises plaguing American health care. It’s the kind of series that generally only exists on cable - trenchant, nonjudgmental, and so steeped in character specificity that it’s not easy to interpret as a general statement of any kind.

The built-in irony of Jackie’s situation is that she’s surrounded by a loving family in Queens and a close-knit staff of professionals at the Manhattan hospital, none of whom can see her psychic injuries. Jackie’s best friend, Eleanor (Eve Best), a brilliant doctor who knows more than anyone about Jackie’s secrets, still doesn’t recognize her despair. Tonight, Jackie continues to follow a treacherous path, in front of everyone’s eyes and yet somehow invisible.

The glue of “Nurse Jackie,’’ of course, has been Falco, whose performance is reserved and honest. On paper, the role of Jackie seems almost impossible to play without relying on broad comedy. She’s a mother of two who curses in a mother-daughter dance class; she’s a wife juggling two men; she’s the cool mentor to a kooky student nurse, Zoey (Merritt Wever). The scenario has the potential to play out like a variation on “Scrubs.’’

And yet Falco resists any urge to go for a laugh - indeed, she resists the urge to go for anything. She delivers a performance dependent on waves of withheld emotion. Her character is charged with all that is unspoken, like a more contemporary take on a “Mad Men’’ character. Indeed, there are comparisons to be made between Falco’s Jackie and Jon Hamm’s Don Draper, since both lead profoundly duplicitous lives, and both somehow remain unknown and unknowable.

Falco is backed by one of the most well-assembled ensembles on TV right now. Each supporting character is amusing and yet dimensional enough to be more than just comic relief. Wever makes Zoey both naive and hardy. Peter Facinelli turns his ridiculous doctor, Coop, into a vulnerable man-child. As Mo-mo, Jackie’s fellow nurse, Haaz Sleiman doesn’t merely play “the gay best friend.’’ Like everything else in “Nurse Jackie,’’ he refuses to take the easy way out.