“All boundaries are conventions, waiting to be transcended”, declares the  young, bisexual British composer Robert Frobisher (Ben Whishaw) near the end of  Cloud Atlas.  That’s the mission  statement for this zany epic – based on a 2004  novel by David Mitchell – which alternates between six separate stories, set in  different historical periods, about the battle for love and freedom.

Besides Frobisher, the other protagonists include a crusading reporter (Halle  Berry), a bumbling publisher (Jim Broadbent), an oppressed clone (Bae Doona) and  a tribesman (Tom Hanks) from a post-apocalyptic future.  Many actors appear in  multiple roles, with heavy make-up sometimes used to alter their race or  gender.

That is as much as can be nailed down about the movie – to attempt a short and succinct summary of plot would be both pointless and frustrating.

What I can say, is that the film sets out to transcend various boundaries, including the boundary  between blockbuster entertainment and art cinema; it also rejects the notion  that a visionary project should be guided by a single individual.  Three of its  segments were directed by Andy and Lana Wachowski, the siblings who brought us  the Matrix trilogy; the other  three are the work of the German director Tom  Tykwer, best-known for Run Lola Run.

But perhaps the real mastermind of the piece is editor Alexander Berner, who has the unenviable task  of linking all the stories together through sound bridges and match cuts.

Does this lumbering machine soar to the skies?  In a word, no. The  performances are often absurdly broad, and it’s unclear how literally we’re  meant to take the notion that different characters are reincarnations of one  another.

But at its best Cloud Atlas has an undeniable charge: it is a film that so boldly  risks incoherence that it requires the viewer, too, to take a leap.

It won’t be for everyone, but truly great movies so rarely are.