Complex sentence: In "Bride of Frankenstein", Henry Frankenstein's former mentor Doctor Septimus Pretorius, proposes to Henry that together they create a mate for his monster, with Henry creating the body and Pretorius supplying an artificially-grown brain.
Split into simpler sentences: In "Bride of Frankenstein", Henry Frankenstein's former mentor Doctor Septimus Pretorius reunites with Henry. Septimus proposes to Henry that together they create a mate for his monster with Henry building the body and Pretorius supplying an artificially-grown brain.