When probed most parents would say that the loss of a child would be their greatest fear. And it wouldn’t matter how that loss came about — whether by illness, unexpected death, or kidnapping — no parent who loves their child would want to experience that sort of hell on earth.

Every parent’s worst fear is realized in the new psychological thriller, "The Forgotten," a well acted if uneven film with a promising set-up that eventually loses momentum yet manages to pack a wallop, however fleeting. Oscar nominee Julianne Moore ("Boogie Nights," "The End of the Affair," "Far From Heaven," and "The Hours") plays Telly Paretta, a married New Yorker coping with the loss of her beloved son, Sam, 14 months earlier in a plane crash.

Still reeling from the unexpected loss, Telly can’t wrap her mind around her husband Jim’s (Anthony Edwards) seeming indifference. So she turns to a psychiatrist (Gary Sinise) to cope with the pain of her grief, only to be told that her son never existed, that he was a mere figment of her overactive imagination. Armed with eight years of precious memories, Telly refuses to accept the diagnosis even in the face of mounting evidence that corroborates it.

By chance she runs into another grieving parent, Ash Correll (Dominic West, "Chicago" and TV’s "The Wire"), who has also lost a child in a similar circumstance, at a local playground they frequent. Ash drowns his sorrows in booze and blocks memories of his daughter, whereas Telly holds steadfast to her memories and cherished mementos. After pleading her case and initially being written off as a headcase, Ash has a sobering revelation and decides to team up with Telly in order to unravel the mystery behind what happened to their kids over a year earlier.

Engrossing psychological thrillers are hard to make and harder to come by. For every "Exorcist" and "Silence of the Lambs" we get twice as many mediocre ones like "Sliver" with Sharon Stone and "Jade" with David Caruso, just to name a few. "The Forgotten" falls somewhere between great and not so; it’s your standard issue Hollywood thriller with better than usual acting.

As they navigate their way through all the pathos, Moore and West shine as the grieving parents who stop at nothing to get to the truth. The equally strong supporting cast includes Alfre Woodard, who’s great as expected though underutilized, as a detective brought into the case who uncovers far more than she bargained for, and Linus Roache as a rather mysterious man who comes into play during the film’s climatic showdown. Sinise and Edwards also do fine work as Moore’s shrink and husband, respectively.

The main point of contention is Joseph Ruben’s direction. What starts out as a promising potboiler, scripted by Gerald Di Pego ("Phenomenon," "Angel Eyes," "Instinct"), starts to lose steam mid-way through the second act. Instead of streamlining some of the plot’s heavy-handed devices and more clearly delineating the film’s arch, he places a strong emphasis on style over substance by relying too heavily on camera tricks and unimpressive CGI that distracts from rather than enhances the action to compensate for an increasingly convoluted story. The end result is a well acted, albeit, stock thriller with little resonance.