Ray is possessed by satanic forces
Ray hears voices in his head that led him to murder a girl when he was young. Those voices also made him kill his mother and father.
The house was built on a graveyard
The house that Jesse and Astrid bought where Ray killed his parents is actually built on a graveyard.
Jesse could hear the voices from the dead
Once they bought the house, Jesse began to hear what he thought to be satanic voices in his head. However, they were actually voices of the dead.
The voices inspired him to paint
The voices inspired Jesse to paint dreadful paintings with satanic meanings and another painting that could have turned into a masterpiece with his daughter burning in fire.
Ray wanted to kill Zooey
Ray’s voices told him that he should kill or sacrifice Zooey. That is why he wanted to see the family and gave Zooey his guitar.
Jesse’s painting foretold the future
The painting of Jesse where he drew Zooey burning was a foreshadowing of future events. He did not realize that until she was kidnapped. (See The Illusionist (2006) Movie Explained)
Leonard represents evil
Leonard convinced Jesse to be late to pick his daughter up, which got her kidnapped by Ray. His car also broke down and he had a flat tire when he went to pick her up.
Jesse tore the drawings
After Zooey escaped, Jesse tore down his painting because he thought it was a bad omen.
Jesse freed the spirits
After Ray burnt in the fire that he created and Jesse saved Zooey, he went to the yard where the graves were and uncovered them. It showed in the movie that the spirits were freed by the light appearing in the sky. (See Sam Was Here (Nemesis) 2016 Movie Explained)
The Devil’s Candy (2017) Movie Explained
The Devil’s Candy Film Summary (2017) | The Devil’s Candy (2017) Explained