Complex sentence: Concerned, Hawkbit goes to check it out again with Hazel and Fiver; they encounter a cave-in and are trapped, but Bigwig believes Hazel, Fiver and Hawkbit have been kidnapped by Efrafa.
Split into simpler sentences: Concerned, Hawkbit goes to check it out again with Hazel and Fiver, but they encounter a cave-in. But Bigwig believes Hazel, Fiver and Hawkbit have been kidnapped by Efrafa.