The story of a crippled thirty-something desperate to get laid - think The 40 Year Old Virgin gets jiggy with The Diving Bell and the Butterfly - isn't the sort of subject you'd imagine would be both exhilaratingly life-affirming and refreshingly funny.
Yet director Ben Lewin's assured cinematic reworking of Mark O'Brien's article On Seeing A Sex Surrogate is a touching gem of a movie largely thanks to subtly dynamic performances from Helen Hunt and John Hawkes.
Hawkes plays O'Brien, a 38-year-old West Coast journalist and poet who - thanks to a childhood bout of polio - spends most of his time inert in an iron lung and unable to walk or even sit up because of the muscle wastage that's symptomatic of the disease.
Yet he maintains a mordantly upbeat view of the world helped in no small part by his pragmatic Catholic priest and buddy Father Brendan (H Macy) and a therapist who both encourage him to act on his heart's desire...and lose his cherry.
This is hardly a done deal as Mark doesn't have a girlfriend, leaving him the bizarrely Californian option of a 'sex surrogate', a physical facilitator who differs from a prostitute in that she doesn't do repeat business and also offers verbal therapy as the deed is done.
The surrogate Mark winds up with is the unabashed Hunt's Cheryl, a no-nonsense mother of one married to a philosopher and a reassuringly practised exponent of the sex surrogate's tactile art.
Their sessions - initially in a friend's flat and then a motel room - are as intimately awkward as you might imagine yet Cheryl's tough and tender approach instils in Mark a new confidence and quiet macho pride while he finds himself responding emotionally to his girlfriend-for-hire.
Lewin (who himself suffered childhood polio) judges perfectly the mood in a story that could easily have gone terribly wrong, assisted magnificently by Hawkes who delicately conveys the frustration of a major disibility and the selfless Hunt's Cheryl, who finds herself in real risk of stepping over the client-customer line.
They're assisted by Macy's generous-hearted priest, a churchman able to amiably see the spiritual dimension of sex and Moon Bloodgood as his good-natured carer.
For a film featuring a life-threatening condition there are no grand gestures or heavy-handed messages, rather a gentle affirmation of life... even if it's treated you terribly.