Lau Ching-Wan in action. [Global Times]

"He knew what they were doing was wrong and would lead to disaster, but failed to persuade and stop his two colleagues. To protect them by covering their secrets, he was forced to commit crimes." Lau explained that the character's cowardice was most attractive and challenging for him.

He said that if the same situation occurred in real life, he would not know how to choose between justice and friendship. "It is hard to betray your friends, but committing crime is also out of the question. So I would be caught in between."

Lau added that he hoped the audience would pity the bad cop after watching the film, which would be a success of his acting.

Playing a 40-something father of four, Louis Koo piled on more than 10 kilograms for his role. Koo remarked that it would now take him more than six months to lose the extra weight. He jokingly complained that Yee always made him look ugly every time they cooperated, as was the case in Protégé, but that this time he had made the decision to push his physical boundaries himself.

He explained that he had not intentionally planned to look unattractive; putting on so much weight was simply better for the role. Koo added that his inspiration came from his wife in the film, who was a plain and frumpy housewife. "When I saw her before shooting, I suddenly realized that my looks were not exactly convincing to be a father of four children. Then I spoke with the directors about gaining weight and having my make-up done to look older."

When researching his role, Koo said that he spent time talking to and learning from people who used to work for the Hong Kong police force's surveillance team. "We could not talk too much about their work because of secrecy regulations, but I learned a great deal about their daily life and their thoughts on the job."

Koo revealed that his biggest finding was that they all talked very fast, which he later replicated in his role. "This is because their job has great tension and danger. They have to meet and follow a lot of people every day, while trying to cover their identity." He explained that the fast talking speed was probably also caused by the pressure that cannot be released by communicating with friends due to reasons of security.

Influenced by his psychologist mother, Daniel Wu has always held a penchant for characters with a dark side. His role in "Overheard," a young and ambitious policeman, is the darkest of the three men.

"His wealthy father-in-law asked him to quit his police job which was insulting to him, so when there came a chance to make a fortune, he went all out and dragged his two friends into tragedy," Wu explained.

Wu said that he tries to deliver a message in every film that he works on. "The message in 'Overheard' is that money is just an extra bonus of life. We cannot sacrifice everything for it."

Wu likened acting to playing tennis. "If your opponent is strong, you will be able to learn a lot."

He admitted that he often chooses a project for its cast. "Working with Lau and Koo was a memorable and benefiting experience."

"Overheard" will premiere on the mainland tomorrow, one week ahead of Hong Kong.

(Global Times July 23, 2009)