Complex sentence: It is soon revealed that Sam's brother died of poisoning caused by plutonium hydride-19 or PuH-19, a deadly gas capable of wiping an entire city's population with just a cup's worth of the chemical.
Split into simpler sentences: It is soon revealed that Sam's brother died of poisoning caused by plutonium hydride-19, or PuH-19. This deadly gas is capable of wiping an entire city's population out with just a cup's worth of the chemical.