Complex sentence: Telly and Ash capture and threaten an agent (Lee Tergesen), who reluctantly reveals that he and other agents are merely helping "them" in order to protect humankind.
Split into simpler sentences: Telly and Ash capture an agent (Lee Tergesen), whom they threaten. The agent reluctantly reveals that he and other agents are merely helping "them" and that they do so to protect humankind.