Piper accidentally brings Mark Chao back. After finding his body and spending time with him she decides to take a look in the Book of Shadows hoping to protect him from Yama. She finds a spell that is supposed to bring about the judgement of a soul and send it to where it belongs; be it heaven, hell or some other plane of existence. What the spell did though is different. It judged his soul alright, but determined it was not his time and reinstated him to his body and reviving him, just as they are loading his body in a van for transport to the morgue. They believe it is a miracle. Piper doesn't realize until a little later when she looks into when his funeral might be. She finds out he is in the hospital in a coma. He wakes a few days later and asks for her. When she sees him awake she cries and kisses his cheek and tells how glad she is that he is awake. He thanks her for returning him to life. She explains to him that while she is happy he is back that the spell she did shouldn't have returned him to his body. It should have helped him to heaven. What Piper doesn't know is that Mark is a future Whitelighter, but he hasn't had the chance to do good and get his status as Whitelighter. With his degree in Molecular Biology he will discover a cure for many forms of Muscular Dystrophy and with his advances they will eventually discover cures for other genetic diseases and helping to prevent certain birth defects. So the people in charge up there high-jacked her spell as a conduit to bring him back. He is still badly burned and has a gunshot wound, but he'll survive. Piper decides she is going to make a potion that will help along his healing. It won't make the healing much faster, but it will help with the pain and scarring. It will make it so he is fully functioning. At first Prue and Phoebe were upset with what Piper had done, especially without consulting them first. Then Phoebe is sent a vision and a message of sorts. She sees a few news articles about different cures for genetic diseases. After analyzing them she realizes the first article is about the discovery of a cure for Muscular Dystrophy. At first she doesn't understand why these visions are important or realize the significance until she sees that date 15 years into the future and Mark's picture is included in the article. It is this that makes her realize that without him they may have never found the cure which means all of those other cures and advances may have never happened either. The message she also receives is that the twist in the spell was not all Piper's doing. The spell she had chosen would have done exactly as it said it would if it wasn't high jacked by those in charge of ensuring his destiny went on as planned.