Director Karan Johar is in unknown territory here. No candy floss romance, no sweet nothings, nobody breaking into song. Just the super intellectual Rizwan, who has Asperger's Syndrome, a form of autism, his halting voice with his inability to communicate, and his many relationships – with his mother, his brother, and yes, Mandira, and her son Sam.

Move over Rahul, Rizwan is here. Shah Rukh makes the transition from the eternal romantic to the intense Rizwan who finds love and loses it some years later when his Khan identity becomes all important in a tense, suspicious America . You sit through three hours waiting to get a glance of Shah Rukh through Rizwan Khan, but it doesn't happen.

If Shah Rukh lives and breathes Rizwan in what is one of his best roles, Kajol as Mandira, the bubbly single mother, is also good – as always. The chemistry between them if not always crackling, then heartwarming.

It's an unlikely romance, not very easy to portray. But it's dealt with a light touch. There they are sitting on either side of the bed after their marriage with Mandira telling Rizwan, who doesn't like to be hugged, that this is something they can't do without touching. It's a scene that could quite easily have gone wrong, but it doesn't.

All credit to Karan Johar for that.

Like a piece of music that slowly rises to grand crescendo, ‘My Name Is Khan' begins with Rizwan as a child with his mother – so good to see Zarina Wahab after such a long time – in an apartment in Mumbai and ends with cheers from the US' first African American president in a crowded rally.

It's from his mother that Rizwan learns his first lessons of humanity; as the 1983 Mumbai riots rage outside; she tells the young boy that the world is divided into good people and bad people.

It is this important humanism that carries Rizwan through from Mumbai to San Francisco where his brother stays, then to the suburb of Banville where he moves in with Mandira and Sam, and even when he is taken to be a terror suspect.

Sam, his ‘only best friend', is subjected to a vicious race attack because he takes on Rizwan's surname. Mandira hits back, saying that the worst thing she could have done was marry a Khan and Rizwan is out on the roads – unable to articulate his feelings but backpacking his way across the US to meet ‘president sahib' so he can tell him: ‘My name is Khan and I am not a terrorist.'

It is a road voyage through a troubled post 9/11 America towards humanism and the essential goodness of the human spirit.

This is a US where chanting the name of Allah gets you into problem, where the word terrorist and Khan in conjunction can put you behind bars. Rizwan moves from being a terror suspect to a nationwide hero who exposes a terror mastermind. And then, the man is with the mission who travels to Wilhelmina that is literally drowning in a hurricane to supervise a heroic rescue mission.

There's Afghanistan and Iraq , Bush and Obama too. The US ' first African American president is voted in and, in that final feel good moment Rizwan meets him in front of thousands of people and his goodness is validated.

Plenty of great one liners. When he is refused entry into a presidential fundraiser for the poor in Africa that is only for Christians, he leaves behind $500 saying: ‘This if for those who are not Christians in Africa .'

The music by Shankar Ehsaan Loy is wonderful. This is not a movie without flaws, it is at least 20 minutes too long for one and flags in the pre-interval period, but here is one directly from the heart. It has a message, in these days of tensions over language and religion, one which needs to be heard.

It is worthy to watch.