While reading a thriller, I anticipate -- and usually get -- a twisty, testosterone-ridden plot. If I'm lucky, there's a strong female character; really lucky, a good sex scene. What I don't expect: a theory of socio-political hegemony centered around the idea of dissent. But Rana Bose's The Fourth Canvas is a novel of ideas as much as a thriller, with enough red herrings to make Agatha Christie proud, and enough progressive ideas to satisfy the most ardent activist.