Complex sentence: It's been implied that secrets involving them will play a major role in the film's plot; recent trailers suggest that Richard Parker was assisting Curt Connors with the research that would lead to him becoming the Lizard.
Split into simpler sentences: It's been implied that secrets involving them will play a major role in the film's plot. Recent trailers suggest that Richard Parker was assisting Curt Connors with the research that would lead to him becoming the Lizard.