David Suchet's Poirot started out in 1989 as a charmingly detailed light comedy turn. It has gained substance with the years- and now the fussy little man is old and weary. He doubts himself and his work- and only his childlike catholic faith sustains him- that and the raging bonfire of his passion for justice. Where once he toddled off screen like Charlie Chaplin, now he exits in hidden tears. It is a remarkable transformation- and I can think of nothing in television history to compare it with. It's as if the series started off Wodehouse and ended up Dostoevsky. Everyone knows whoddunnit on the Orient Express, so why not- to save redundancy- turn this most famous of murder mysteries into Crime and Punishment? Why not? Because the material is just too flimsy to sustain the weight. That's the sensible answer. But the sensible answer is wrong. And the reason it's wrong is because Suchet- with his command of stillness and his furious eyes- is one hell of an actor.