Complex sentence: Callie becomes friends with horse trainer Rafe Acuna (Adam Beach), who teaches her to ride, and she helps him discover that something is seriously amiss about Kia, a "wild" thoroughbred horse.
Split into simpler sentences: Callie becomes friends with horse trainer Rafe Acuna (Adam Beach), who teaches her to ride. She helps him discover that something is seriously amiss with Kia, a "wild" thoroughbred horse.