In The Time Machine, why was it ill-advised of the Time Traveler to set a fire and leave it?
I think this is the answer you are looking for. The Traveler has set the fire to destroy the humaniods and return with Weena to the Machine. But the fire and heat become too intense, and he is separated from Weena. Faced with the choice of death at the hands of the approaching Warlocks or escape, he chooses the latter and Weena is left behind.