The start of this is breathtaking, switching suddenly from Emma Thompson's scientist pronouncing a cure for cancer, to a deserted New York, making it immediately apparent that something, somewhere has gone horribly wrong. Gradually, we find out that the vaccine mutated, becoming an unstoppable plague which has left Dr. Robert Neville (Smith) as, apparently, the last man alive. He spends the days researching a cure and roaming the deserted streets, and his nights cowering in the bathtub - because the disease doesn't so much kill its victims are turn them into murderous, cannibalistic animals, who own the darkness. His sanity is gently eroding; he talks to mannequins, and is haunted by the loss of his wife and daughter. Can he find the cure before sliding into madness?
That would be a fascinating film in itself; unfortunately, the film doesn't go that route, opting instead to show us - and this shouldn't be a spoiler for anyone familiar with Hollywood pap - that he is not actually the last man alive. The film crashes, hard, from this point on, spiralling down to a finale that makes no sense from Neville's point of view [the survival instinct apparent in the first hour suddenly evaporates] and ties up the loose threads in two minutes. The End. This leaves you contemplating the plotholes, such as where the eight-million or so dead bodies that should be littering New York went, or how - since the bridges were blown up - the non-last people on Earth got back into the city. This would likely have been far better in the original plan, where Schwarzenegger was the hero and Ridley Scott the director. While better than I, Robot, Smith clearly needs to stay away from SF adaptations starting with I, but we should probably expect Island of Dr. Moreau in 2010.