Cathleen Young’s adaptation of Barbara Taylor Bradford’s “Everything to Gain” zeroes in on a woman’s melancholy after her perfect husband and their two tots are gunned down, and how, rallying, she seeks revenge. Hard-to-swallow, stylishly mounted drama tracks her story under Michael Miller’s loose direction; as she stands here, main character’s a 1950s Redbook reject. Mallory (Sean Young) marries dynamic, wealthy Andrew Kewick (Charles Shaughnessy). Six years later, in a delightful interlude about their home life, they revel in their two little girls, oceans of money, nothing but happy days ahead. But this happiness stops when Andrew and the kids are slain by a pair of N.Y. thugs. Mallory, numbed and alone, insists she can’t go on. Her nicely disarranged mother (Joanna Miles) and her sensible English mother-in-law (a welcome Samantha Eggar) try helping her, but she can’t come around. Mallory’s best friend has rescued her from suicide. Mallory hallucinates about her dead husband and children, but no one insists on medical, psychiatric or ministerial aid. In deep depression, she stares into space. Best-written seg involves Mallory’s talk with an aging, wise English houseman (intelligently played by John Dunn-Hill). That scene makes sense; otherwise, Bradford and company let the despondency amble on untreated. Mallory’s electric shock therapy is tough-talking N.Y. cop Michael DeMarco (Jack Scalia), who’s doing what he can to find the killers. A year goes by, and Mallory asks him to let her help him. He semi-hesitantly (and incredulously) breaks a couple of cop rules; Mallory, schmoozing with a witness (Ellen Cohen), finds the name of the killer’s accomplice. The vidpic has taken on a bizarre attitude toward police work. The refined Mallory comes to Michael because she doesn’t want to be alone one more night. Miller directs Mallory and Michael in a shoddy, embarrassing romantic interlude. Despite such action, Young’s a graceful beauty who dignifies her role. Shaughnessy is particularly fine, and a restrained Scalia does a solid job despite the silly demands. Miles, her gray hair shoulder-length, gives the curious role of Mallory’s mother substance. Eggar’s a pleasure as Andrew’s strong, gracious mother. Paul Pompian’s production looks fine, and designer Anne Pritchard has resourcefully substituted Montreal for Manhattan and for the English countryside. Pierre Mignot’s lensing and Gordon McClelland’s editing are superior. James DiPasquale’s score reflects the lushness, if not the nonsense, of the telefilm.