Penn's thrilling Pledge

The Pledge features an impressive cast

By the BBC's Caroline Westbrook

It is a safe bet that any film directed by Sean Penn will be a far from feelgood affair, and The Pledge is no exception.

Like his two previous efforts from behind the camera, The Indian Runner and The Crossing Guard, this is grim stuff.

However, it is also far more accomplished than his previous pictures, and is further bolstered by Jack Nicholson's terrific, tortured central performance.

Here, Nicholson stars as Jerry Black, a smalltown cop on the brink of retirement - so much so that he is actually at his leaving bash when news comes through of a vicious child murder in the neighbourhood.

Wright Penn puts on an impressive performance

When he accompanies his colleagues to investigate, Black finds himself promising the girl's grieving mother that he will track down the killer.

Indeed when the prime suspect, a mentally disabled drifter (Benicio Del Toro) is coerced into a confession, it looks to be an open and shut case.

But Black is convinced there is more to this one than meets the eye - and he embarks on a near obsessive investigation of his own.

However, events take on a sinister new twist when he befriends a single mum (Wright Penn), whose eight-year-old daughter bears a frightening resemblance to previous victims.

Although this seems on the surface to be a straightforward whodunnit, it offers far more than your average thriller.

Jack Nicholson is on top form as cop Jerry Black

The plot throws in endless twists and turns and suspicious characters, half of whom appear to be harbouring psychotic tendencies.

This will leave you changing your mind about the killer's identity from one minute to the next.

The supporting cast is superb - Wright Penn stands out, as does Aaron Eckhart as Black's by-the-book boss, who resorts to some seriously bizarre police procedures to secure the confession he wants from Del Toro's would-be murderer.

And at its core is Nicholson, in top form as the cop clinging to his sanity, who takes his new quest to such extremes (when he really should be out fishing) that it leads you to question whether he has genuinely stumbled upon an unsolved mystery or is simply losing his marbles.

In fact, Penn builds the tension so superbly and keeps the audience in suspense to such a degree, that the film's final, ambiguous twist comes across as somewhat unsatisfying, and may well disappoint audience members hoping for a more traditional denouement.

That said, this is still the kind of compelling, complex thriller that comes along all too rarely. And as such, it is well worth the ticket price.

The Pledge is on general release in the UK from Friday 11 October.