"Suspense films have been made in the past but this is for the first time that a suspense trilogy has been attempted," said Mahadevan.
The film stars Shreyas Talpade and Tusshar Kapoor in the main leads.
"The casting of 'Agar' is very interesting and intriguing. It will be a complete departure for both Shreyas and Tusshar. Both are playing interesting characters and it will break their respective images.
"This will be Shreyas' real mainstream film and even Tusshar's character is completely unpredictable. Tusshar got really excited when he heard the script," said Mahadevan who wishes to keep the story under wraps.
"Agar" will go on floors in November and will release after the Cricket World Cup, (April end) next year.
And "Anjaam", part three of this suspense trilogy, is in the scripting stage and the shooting is expected to start in May next year.