The novel by Patrick McGrath on which “Asylum” is based may have some subtext that gives its tale of an unhappy wife who abandons her family for a mad passion a deeper resonance, but in this adaptation by David Mackenzie (from a script by Patrick Marber and Chrys Balis) it comes across as essentially an elegant but dramatically opaque period soap opera, an old-fashioned woman’s picture decked out like an episode of “Masterpiece Theatre,” but with a bit of steaminess added to distinguish it as big-screen fare.

Natasha Richardson stars as Stella Raphael, the beautiful wife of Dr. Max Raphael (Hugh Bonneville). As the story opens in the late 1950s, the two arrive with their son Charlie (Gus Lewis) at the rural facility for the criminally insane where Max has taken a position that may involve succeeding the institution’s aging director (Joss Ackland)–much to the chagrin of long-time staffer Peter Cleave (Ian McKellen), who believes he should ascend to the top post. Though Stella is affectionate toward her son, she’s a rebellious sort of woman who obviously feels stifled in her almost businesslike relationship with her husband, and it’s not long before she’s become involved in a sultry fling with Edgar Stark (Marton Csokas), an artist and long-time patient whom Dr. Cleave allows to assist in repairing the Raphaels’ greenhouse (and who quickly befriends young Charlie). The duo’s initial coyness soon develops into a lusty affair, setting tongues wagging throughout the primly controlled staff and threatening Max’s status. And when Edgar escapes, Stella contrives to meet him at his London refuge and, when her trysts are discovered, abandons her family to join him there–even though she’s well aware that he was institutionalized for killing his wife in a fit of jealous rage. Things do not turn out happily for them. Edgar’s madness reemerges, Stella is captured and returned to her ruined husband, her efforts to reconnect with Charlie lead to tragedy, and Edgar comes looking for her again. By the last act Stella herself has been committed to Dr. Cleave’s care, and though she still pines away for the (recaptured) Stark, Cleave longs for her himself.

This is a lot of territory to cover in little over ninety minutes, but the curious thing about “Asylum” is that it seems both rushed and solemn. The picture is literally stuffed with incident, but it all seems arbitrary and disconnected because the characters aren’t drawn much beyond the sketch stage and their motivations remain obstinately obscure. Yes, we realize quickly that Stella’s been forced to repress her wild side, but that hardly explains her willingness to embrace self-destruction, and Cleave’s ambition is clear, but whether his longing for Stella is anything more than a desire to take everything his rival possessed is never revealed. In short, more attention seems to have been lavished on sets and costumes than on the people who inhabit them, so that while the film looks authentic in every insignificant detail, it never seems remotely real from an emotional standpoint. Even such fine actors as Richardson and McKellen appear to be striking poses rather than registering genuine feelings, and Csokas and Bonneville are even more stilted and unconvincing. Judy Parfitt, meanwhile, is a sheer caricature of snobbish rectitude as Max’s unforgiving mother, and the usually reliable Ackland putters about too much as the elderly director. Only young Lewis manages to be natural and unforced as the Raphaels’ son. As for the intimate scenes between Richardson and Csokas, they’re less explicit than those in Mackenzie’s last film, “Young Adam,” but like them they strike no real sparks.

A good deal of craftsmanship and intelligence has been expended on “Asylum”–Laurence Dorman’s production design, Consolata Boyle’s costumes and Giles Nuttgens’ cinematography are all admirable. But the end result is a film that, while visually lustrous, is dramatically parched and claustrophobic.