wait, just in from wikipedia. He doesn't stay a monster
here's how the arc goes down:
Jason has resurfaced in New York City, patrolling the streets as a murderous version of Nightwing. He executes a kidnapper, nearly beats a rapist to death, and even slices Dick Grayson's hand when the two spar on a rooftop. Jason shows no intention of giving up the Nightwing persona, and continues to taunt Grayson by wearing the costume and suggesting that the two become a crime-fighting team. Grayson naturally refuses to join his side and methods of crimefighting. Not long after the two Nightwings meet up, Jason is captured and imprisoned by unknown mobsters, leaving a very troubled and reluctant Grayson to rescue him. Jason is rescued by Grayson, however he has briefly acquired the ability to transform into an insectoid and swallow people. After helping Grayson defeat the Pierce brothers, Jason leaves New York City and the Nightwing mantle to Grayson, along with a telegram telling Grayson he has returned to normal and still considers them family.