Complex sentence: Acting as an audience surrogate, she notices Jack is following her and she is led to investigate him and his team, eventually discovering by following him to his base that they are Torchwood, a team of alien hunters.
Split into simpler sentences: Acting as an audience surrogate, she notices Jack is following her and subsequently investigates him and his team. She eventually follows Jack to his base that he and his colleagues are Torchwood, a team of alien hunters.