Grue is described as a man who looks older than his years, but still a little too old for mercenary work. He has curly hair like his daughter, and a rasping, rattling laugh. He smokes often and wields a Python magnum.
Grue is a father of three daughters. His oldest daughter is Jessica. His middle child is Tiki, and the youngest is Nesty.
Tony and Grue are hired along with several other mercenaries to protect an unsavory character on his way out of the country. En route to the port, the caravan they are traveling with is ambushed. Tony at first fights the opposing side, but when their caravan launches a counterattack against the more numerous assailants, he and Grue hide until the gunfire stops. After the battle, the corpses of the dead men rise and attack Tony. Grue watches, terrified, as Tony mows down the zombies.
Afterwards, the two go home to Grue's house. Tony makes a mess at the dinner table with Grue's younger children. After dinner is over and Grue and Tony have a moment to themselves, Grue laments how hard it's been on Jessica since his wife passed away. He asks if Tony could treat Jessica to a date, as a favor to him and a thanks to Jessica for her hard work.
When Tony is paired off to work with Gilver, Jessica falls ill and goes to the hospital. Grue turns to assassination work to pay for his daughter's care. One of the assassin jobs he takes turns out to be not so easy and he encounters Gilver, who is intent on murdering him after Grue discovers him. The two fight and Gilver wounds Grue's right shoulder. Grue's last thoughts turn to Jessica and Tony, thinking of the latter's brilliant smile and how wonderful and beautiful the former is. He dies trying to blow up Gilver with a grenade.
After Grue's death, Tony learns that Jessica has been hallucinating about demons. Tony goes to the sanatorium where she was admitted and finds it transformed into a portal to the demon world. After fighting his way to the deepest part, he finds Jessica. She is fused with a demonic tree that is using her pain and despair to grow a path to the human world. Tony ends her suffering, and later uses his own savings to open bank accounts for Grue's remaining daughters, Tiki and Nesty.