Complex sentence: After discovering Jay is dying, Caitlin, along with Harry, develops "Velocity-6" to grant temporary speed and perfects it to Velocity-9 to get Jay's speed back and repair his damaged cells.
Split into simpler sentences: After discovering Jay is dying, Caitlin, along with Harry, develops "Velocity-6" to grant temporary speed. She perfects it to Velocity-9 to get Jay's speed back and repair his damaged cells.