Complex sentence: In "Zippleback Down" Torch returns as a fully-grown adult and befriends Toughnut; he then helps Hiccup and the others put out a forest fire, after which he departs again.
Split into simpler sentences: In "Zippleback Down" Torch returns as a fully-grown adult and befriends Tuffnut. He then helps Hiccup and the others put out a forest fire, after which he departs again.