Amitabh Bachchan is in a hysterical rage. But only on camera - for Ram Gopal Varma's "Darna Zaroori Hai".

"I'm shooting the whole day and night with Mr Bachchan at Filmalaya. Why don't you drop in?" my friend Ram Gopal Varma invites me.

Watching Varma direct Amitabh is an experience that can't easily be forgotten.... or outdistanced.

An eerie silence envelops Floor 1 at Filmalaya. The film is being done in live sound. Every syllable of Amitabh's baritone reverberates across the floor in booming glory. On the teak-brown set representing a bedroom and a study room at a hill station, equipped with an aquarium and a study table cluttered with books, a coffee cup and a half-filled glass of orange juice, Amitabh is looking dapper. His perfectly fitting wig is a chalky grey colour that suits him perfectly.

"I know how much you love wigs," I quip as he greets me warmly.

"Kya karen, pet ke liye sab kuch karna padta hai! (What to do, one has to do everything to earn a living)," he quips.

We had met the night before for dinner. The morning after, he looks as fit as a fiddle and ploughs through the 16-hour non-stop schedule doing some of the most harrowing shots I've ever seen any actor doing.

The sequence has Amitabh and Riteish Deshmukh (who seems to be quite a Varma favourite after "Naach") caught in a bizarre guru-shishya (teacher-pupil) confrontation. As the petrified and shaken Riteish tries to come to terms with the raging Amitabh, it's quite clear that something is seriously amiss in their characters' lives.

As Amitabh's voice rises to a quivering crescendo, Riteish grabs hold of his belongings on the table and begs off, saying his father is waiting at home.

Amitabh Bachchan stares wryly at his student. "You think I'm making it all up? Look at me! There's someone who's actually trying to finish me off. It's.... him!" And he points to the mirror image in front of him, freaking Riteish out even more.

Kiran Reddy, the magician behind the camera from "Naach", cans the shots with a look of blissful contentment.

Watching AB shoot dramatic scenes is an experience beyond words. He goes over his lines diligently, asks for rehearsals, re-positions Riteish to a confrontational radius and gets into a thick woollen pullover in that stuffy windless studio to rage at his student like a wounded hero from a Shakespearean tragedy.

Riteish continues to shake after Varma cans the shot. Is it the character or just the experience of sharing screen space with the mighty Amitabh Bachchan?

"Both!" laughs Riteish. "It's an honour beyond words to work with Mr Bachchan. I'm choosing my roles as carefully as possible. And it doesn't get any better than this," he says, as he returns to the set to sit on the floor next to AB who's looking at his lines sitting on a chair.

Where does the energy and passion come from? AB brushes off the compliment. "It's part of my work. I've to finish my episode before flying to Delhi."

Throughout, Varma remains as stoic as a monk in a discotheque. He's respectful but not docile before the awesome superstar. "This is the second story in my 'Darna Mana Hai' sequel.

The first story has been directed by Sajid Khan. I'm doing this one. So what if 'Darna Zaroori Hai' didn't work? I still wanted to do a sequel. As you can see, Mr Bachchan's presence does give the sequel a certain edge, don't you think?"