In a strange twist of irony, a Hollywood movie borrows from a Hong Kong film hugely inspired by American crime classics. Martin Scorsese's "The Departed" does seem to be influenced by "Infernal Affairs" - the Hong Kong film released in 2002.

Scorsese has simply complimented the original. The film's script retains the essence of the earlier film but also adds much more flesh to it.

This is Leonardo Dicaprio's third film with Scorsese after "Gangs of New York" and "The Aviator".

The plot revolves around Billy Costigan (Dicaprio), a cop pretending to be a crook and Colin Sullivan (Matt Damon) doing just the opposite. They both soon find themselves embroiled in situations where it becomes increasingly difficult to tell the good from the bad, as the line gets more and more blurred.

Colin has been trained to be a mole by his gangster mentor Frank Costello (Jack Nicholson). Billy, on the other hand, realises that he will never be a good cop and so agrees to go undercover and join Costello's gang. As the story progresses, the pressure on the two becomes unbearable as they have to do things completely against their true nature ... and they fail.

The movie's thrill factor is served well by a series of coincidences like when Billy and Colin fall for Madolyn (Vera Farmiga), the psychiatrist who treats Billy but is already involved with Colin. With a story where the main characters have to lie their way out of every situation, there have to be enough twists and the plot's ends are not tied up till the very last frame of the film.

One of the strongest points of the movie is the acting. Both Dicaprio and Damon are excellent. They even begin to start looking like each other as they become more and more entrenched in their deception.

Jack Nicholson, who is a legend in his own right, is brilliant in this role where he sinks his teeth with devilish charm and delight. His performance is electrifying in what is surprisingly the first time he has teamed up with Scorsese.

Farmiga convincingly portrays a great mix of sex appeal and intellect.

Alec Baldwin, playing the arrogant policeman, has some of the funniest moments with Wahlberg's Dignam. Martin Sheen plays the father figure Captain Queenan - the warmest character in the movie. He may not be ruthless but he is honest and dedicated.

The violence in the film jarring at times but seems to be judiciously used for the right impact. It is not blood soaked as much as sprinkled. It fits in well with the gritty nature of the place, profession and people in the film.

Scorsese has always been a director who has tackled grandiose themes like sin, redemption and loyalty. But in "The Departed", he sticks to a more narrative framework but still tackles the themes albeit more subtly.

The script is by William Monahan, which comes as a pleasant surprise considering his last script was for the bloated, flat and insipid "Kingdom of Heaven".

Howard Shore contributes to the score but is helped by Scorsese's brilliant use of pop music, which is a trait of all his movies. There is an interesting mix of The Rolling Stones, John Lennon, the rapper Nas, Van Morrison and the Beach Boys.

"The Departed" is pure entertainment in the mould of an American crime classic, but is sure to please audiences the world over.