A turnback will work IF you have enough energy (speed/height). Therefore, in theory the turnback option switches from 'No' to 'Available' at a set point in the climb out. Once 'Available' you do need to ensure you react promptly, turn the correct way (wind dependant) and as Mogwi highlights - avoid the stall. If you're not sure, don't risk turning too tightly too near the ground.
Unless over 'inhospitable' terrain, a correctly handled engine failure should result in nothing more than injury and not death, even if the airframe is never going to fly again!