Do not mistake The Greatest for a movie about Muhammad Ali. And do not think its ambitious title indicates its overall quality.

Distinguished by a gripping pre-titles sequence and a remarkably nuanced performance by Pierce Brosnan (who executive-produced), The Greatest is a group portrait in grief, inconsistently told. The tone of writer/director Shana Feste wavers wildly from deeply felt empathy with the mourners to melodramatic exploitation of them. Not only are the plot holes so big you can drive a truck through them, Feste literally drives a truck through them.

Before the titles roll, a youth loses his life in an avoidable accident. Compounding the tragedy for his parents (Brosnan and Susan Sarandon), kid brother (Johnny Simmons), and the dead boy's girlfriend (Carey Mulligan, dimpled darling of An Education) is that he is taken at the happiest moment of his life.

The theme of Feste's film, powerfully dramatized in an early scene, is how family members who might help one another mourn retreat to grieve in isolation.

Feste characterizes the leads as the Three Bears of Grief with the girlfriend as something of a Goldilocks interloper. Hyper-expressive mom can't stop crying; repressed dad won't let himself feel; baby bro self-medicates with pot. In other words: too soft, too hard, too stoned.

Rather than rely on one another for emotional support, each survivor initially seeks solace in a stranger. There's something mechanistic about the way Feste structures her film (nicely shot by John Bailey) about people taking the long way around before coming together. Yet Brosnan, who finds the truth in his character, is quite affecting. And Mulligan, gamely defining a surprisingly undefined young woman, is like a sunbeam piercing the gloom.

The Greatest ** (out of four stars)

Written and directed by Shana Feste. With Pierce Brosnan, Susan Sarandon, and Carey Mulligan. Distributed by Paladin.

Running time: 1 hour, 40 mins.

Parent's guide: R (discreet sex, profanity, brief drug use, mature themes)

Playing at: Ritz at the BourseEndText

Contact movie critic Carrie Rickey at 215-854-5402 or crickey@phillynews.com. Read her blog, "Flickgrrl," at http://www.philly.com/philly/blogs/flickgrrl/