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