Complex sentence: After presenting the ring to Leela, he invites her to meet him atop the Vampire State Building at 6:30 pm if she agrees to marry him; if she does not arrive, he will infer rejection.
Split into simpler sentences: After presenting the ring to Leela, he invites her to meet him atop the Vampire State Building at 6:30 pm if she agrees to marry him. If she does not arrive, he will infer rejection.