Caine's vitality is one element that makes 'Sleuth', a gala presentation at this year’s Toronto International Film Festival, so stunningly different than the 1972 movie that was also based on the Anthony Schaffer play of the same name. That one also starred Caine, but in the role of the upstart hairdresser Milo Tindle that Law occupies now.

Caine has taken over the character of the cuckolded mystery writer Andrew Wyke, then played by Sir Laurence Olivier. Olivier's Wyke was an old man and addicted to playing games, at one point forcing his rival to don a clown costume. Caine's Wyke is far more virile and his gamesmanship is more cunningly manipulate, as he plays with Tindle's head and otherwise attempts to assert his dominance over his young rival. There is also a homoerotic element to the new film that is wholly absent from the original.

In fact, Caine insists that this 'Sleuth' is not a remake at all and that he would not have become involved with the new movie if he thought that it was. "I never would have remade the Schaffer script, because I thought Joe Mankiewicz had done a perfectly good job of that and you couldn't improve on it," Caine tells FilmStew. "There would be no point to it."

It was Law, wearing his other hat as producer, who got the ball rolling on the new Sleuth, asking legendary playwright and screenwriter Harold Pinter to have a crack it. Though seriously ill with cancer, Pinter agreed. He had never seen the original film, so he adapted strictly from the text of Shaffer's play. The result was a revelation to the man who knew the property so well, Caine.

"There isn't a single line of dialogue in there that was in the first one – there was never any feeling of doing a remake for me," he marvels. "I never had any sense of having a remake, of having been there before, because I hadn't. It was so completely different as to be unrecognizable."

Branagh had his own epiphany over what Pinter had written when he asked Caine and Law to come to the soundstage for a reading prior to shooting the film. "The rehearsal is all about the effort to make it look effortless," he explains. "The idea is to be as completely spontaneous as you can on the day. If you really work hard, you can change things at the last minute and the boys can roll with it. Ultimately, my goal with the rehearsals is to get the boys to the point where they feel like there is a completely improvised quality to something that they have prepared so, so well that they can surprise each other in the moment."

But it was only during that reading that Branagh discovered that the sense he had of the story from reading the screenplay was not entirely correct. He thought he was making a serious drama, but as Caine and Law put each other through their paces, Branagh realized how much comedy Pinter had injected into the story.

"From the word go, I began to realize, 'This is funny,'" Branagh explains. "This is very much funnier. When I first read it, I was getting thriller and suspense and sinister and earnest and then the two boys arrived and I understood that it could be extremely [humorous]."

The new 'Sleuth' is a sleeker animal than the 1972 feature. At an efficient 87 minutes long, it is an hour shorter, a shock to Caine, who laughs, "I said to myself, 'What the hell did we do for the other hour?' The plot was all the same in the other one. I thought, 'Where did the other hour go?' It was weird."

Branagh jokes that it was Caine having to get in and out of the clown costume that ate away at that hour. "It was those flat feet!" Caine chuckles in agreement.