Complex sentence: He is prevented from seeing the mother by a female Secret Service agent, but when he shows the agent the earring, the agent recognizes it as one she herself gave Laura, and admits that a cover-up is occurring.
Split into simpler sentences: He is prevented from seeing the mother by a female Secret Service agent. But when he shows the agent the earring, the agent recognizes it as one she herself gave Laura and admits that a cover-up is occurring.