Matt Campbell is a teenager afflicted with cancer. He is participating in a treatment trial at a Connecticut hospital, so his family rents a house near the hospital. The guy who rents them the house mentions that the house has a "bit of history", which turns out to be a huge understatement.
As soon as they move in, Matt starts to have visions, but he and his parents are reluctant to tell the doctors, because then he would not be able to participate in the next stage of the trial. They eventually find out that the house used to be a funeral home. They also find some pictures matching the visions that Matt has been having. As the previews indicate, the problem is the dead people's spirits are still there. Matt enlists the help of one of his fellow patients, who introduces himself as "I'm a Reverend". He does not wear a roman collar, and he doesn't identify himself as a priest, so it is not clear if he is Catholic, but he does perform some sort of an exorcism to remove the spirit he believes to be the problem. Later, he realizes there is more "housecleaning" needed to get rid of the rest of the spirits.
The family does turn to prayer. They pray together, and at one point, Matt's mother is saying the rosary and looks up and says "you can't have him". She is not ready for her son to die, and later the doctor tells them just how close Matt is to death. In the end, Matt figures out what is needed to rid the house of the spirits.
The main content warning is gore. There are several gory scenes, with slime coming out of people's mouths. Also some gory scenes from when it was a funeral parlor