Angelina Jolie's towering performance dominates this finely layered drama, writes Michael Dwyer

AS SHAKESPEARE observed of Cleopatra, age cannot wither Clint Eastwood, nor custom stale his infinite variety.

Now 78, Eastwood has been setting the bar high for himself as a director in recent years with such accomplished films as Mystic River, Million Dollar Babyand the companion pictures, Flags of Our Fathersand Letters from Iwo Jima. His masterly new film, Changeling, sustains that remarkable standard, and features Angelina Jolie in what is by some way the outstanding performance of her career to date.

Changelingopens in Los Angeles in March 1928, introducing Christine Collins (Jolie) as a caring mother to her nine-year-old son Walter (Gattlin Griffin), whose father left home when the boy was born. Discovering that Walter has been in a fight at school, she advises him never to throw the first punch, but always to throw the last. We soon learn how tenacious Christine can be when she comes out punching.

Returning home from work as a telephone exchange supervisor, Christine is alarmed that her son is missing. There is an exchange of a different form when, after five long months of despair mixed with hope, she is told by the LAPD that Walter has been found in Illinois. As soon as she meets the boy, she realises that he's not her son, even though there is a strong resemblance, and her suspicions are confirmed when she detects significant physical differences.

Not for the first time in a movie, the LAPD is depicted as steeped in corruption. Determined to mark the case closed and claim credit for finding Walter, the police ignore the protests of a mere woman. Her only ally is a pastor (John Malkovich) who has campaigned from the pulpit and on his radio show against the vice and incompetence within the police force.

And that is just the beginning of a fascinating film whose scenario expands and diverges in unexpected directions to address a range of themes, some deeply unsettling and at least as pertinent today. The screenplay, by J Michael Straczynski, is exceptional in structure and dialogue, as this meticulously shaped drama unfolds to reveal a succession of surprises.

Eastwood treats these narrative developments in classical film- making style and with a characteristic understatement. His direction is matched by the low-key score he composed to accompany the accumulating dramatic tension.

Another striking illustration of Eastwood's measured approach is the untypically restrained performance from Malkovich, which is all the more effective for that and for resisting the cinema convention of treating evangelists as shrill, one-note caricatures.

In the pivotal role, Jolie has never been so subtle and expressive, inhabiting her role with an alert intelligence to capture the turmoil, fragility and determination of a woman patronised, dismissed and cruelly treated by patriarchal authority figures.

Eastwood surrounds her with an exemplary cast that most notably features Amy Ryan during a harrowing sequence in a mental hospital; Eddie Alderson as the boy who claims to be Walter; Michael Kelly as one of the few honest LAPD detectives; and Jason Butler Harner in an arresting portrayal of a disturbed young man with no moral compass.

One of the many revelations in Changelingis that it's based on fact, affirming the adage that truth can be stranger than fiction.