Complex sentence: In a flashback, during the first encounter between Ursus and Gwynplaine., the boy is clutching the nearly-dead infant, and Ursus is outraged that the boy appears to be laughing.
Split into simpler sentences: In a flashback, we witness the first encounter between Ursus and Gwynplaine. The boy is clutching a nearly-dead infant, and therefore Ursus is outraged that the boy appears to be laughing.