Touted as one of the best Hong Kong cop films of all time, "In The Line Of Duty 4" delivers breathtaking action with immaculate choreography and flawless execution by its stars Donnie Yen ("Blade 2", "Iron Monkey") and Cynthia Khan as two cops from both sides of the Pacific on the trail of a drug trafficking syndicate. Khan and Yen discover to their dismay that the syndicate has more than one insider working in the law enforcement agencies. As they break the rules to save a witness, the two find themselves pursued by American assassins, Hong Kong gangs and the law.

"In The Line Of Duty 4" scores a 10 out of 10 for action and equally as much for the outstanding performances of its cast.

They found actress Cynthia Yeung, changed her surname to Khan and Starred her in the disappointing In the Line of Duty 3.

For the next instalment in the series they teamed her up with then up and coming young star Donnie Yen. And came up with one of the best cop action films of the 1980's.

An innocent immigrant working in America stumbles across a gang assassination and wrongly gets accused of murder. After saying he was just a witness and that he could identify the killers he is relentlessly pursued to Hong Kong by the gangsters and the police.

When it is discovered one of there own is corrupt it is up to Donnie and Cynthia to save the witness and bring the criminals to justice.

The somewhat weak plot is itself just a series of excuses to display some amazing fight scenes.

Cynthia Khan displays some superb fighting skills and has one memorable fight on top of a moving ambulance! Donnie Yen here proves just what a superb Martial artist and actor he is with a series of fights especially with bad guy Michael Woods on top of the old Kai Tak airport in Hong Kong.

Director Yuen Woo Ping shows what a master choreographer he is with amazing action scenes.

Forget his later wire fu efforts in movies like Tai Chi Master and The Matrix here he shows what he can do without the aid of overused wires and special effects.

One of Donnie Yen's best movies so far. Check it out.

What this film is really about is non-stop action and with Yuen Wo Ping directing it is very well done. The producers must have imposed a rule there must be some action at least every five minutes and sometimes there is not even that much of an interval. Both Donnie and Cynthia have some absolutely terrific action scenes that allow them to display their skills and they have some very tough opponents to go up against.

There are so many action scenes here that would be considered good in most films - but are almost mundane in this one. That is because the bar is raised so high by a few truly exceptional ones. The scene with Cynthia fighting on top of, on the side of and nearly beneath the moving ambulance is great stuff as is her fight in the elevator shaft against the gweilo blonde female.

Donnie has a few showcase scenes that display some amazingly quick moves and in an early fight he uses one of his patented moves in one jump he kicks one guy going up and a second guy while coming down. Then in the finale, while overlooking the old HK airport he has a classic match up against muscle man, Michael Woods, that goes on for quite a while and is quite astonishing in its ferocity.

In fact much of the film has a sense of visceral in your face action to it that leaves even the winners exhausted and badly beaten up. Nothing comes easy in this film. Though opinion seems to be divided upon which is better In the Line of Duty III or IV I would have to cast my vote for three. This sequel does have more action but I think the other had a more interesting story and the wonderfully charismatic brooding presence of Michiko Nishawaki. As good as Donnie is in his action scenes, I found his character insufferably irritating as it was suppose to be admittedly and thought the brutal treatment of the witness/suspect to be a bit farfetched. In any circumstances though, this would be considered a classic action and girls with guns film.