Complex sentence: When they arrive at the sanitarium, due to a comedy of errors, the doctors commit Veta instead of Elwood, but when the truth comes out, the search is on for Elwood and his invisible companion.
Split into simpler sentences: When they arrive at the sanitarium, a comedy of errors ensues. The doctors commit Veta instead of Elwood, but when the truth comes out the search is on for Elwood and his invisible companion.