Laura and her brother Jacko came across a strange man on the way home from school. He offered Jacko a stamp that appears to have his face on it. When he stamped Jacko's hand it burned for a second but then went away straight after.
Once Jacko and Laura had gotten home his hand had gone all veiny and red. He felt very sick and he got taken to hospital after that night. Laura knew Jacko's sickness had something to do with that old man.
So she went to see one of her classmates Sorenson (sorry) Carlisle whom she swore was a witch. She told him about the stamp, about the sickness, she told him everything he would need to know to be able to help Jacko. He did in fact know what had happened to Jacko.
After Sorry told Laura that the man was possessing Jacko Laura took great caution in protecting her brother. The man showed up at their house one day and Laura quickly figured that the man couldn't come inside unless he was invited. While Laura was trying to get the man to go away, Jacko placed his hand on the hot stove and burned both his and the old man's hands.
Once Jacko went back to the hospital Laura went to Sorry's house because she was worried and didn't know what to do. Sorry, his mother and his grandmother tell Laura that the only way to kill the spirit and free Jacko would be to turn her into a witch.
After Laura agrees, she goes to defeat the man, resisting the temptation and gets rid of the thing that was holding her brother captive.