Haunted - RadioLab

Dennis had a hard time leaving home. After leaving college, he spent most of his 20s living with his parents. When he was 28, he was finally ready to leave the nest. Months after he left, his mother was diagnosed with breast cancer. A short while after his mother passed away, his father was diagnosed with prostate cancer, and passed away.

After he lost both his parents, he was left with the house he tried to leave. He moves back in at the age of 32, and started doing renovations to the home.

Night after night, he dreamt that his parents came back to the house, and undid what renovations he had done to their house. Three separate friends came by the house, each telling him they felt a strange presence.

Paranormal investigators came by to see what this presence was. Dennis had always been a skeptic when it came to hauntings. He started believing when the lead investigator saw a presence that looked like Dennis's dad. He communicates with him through a flashlight. If his dad answers "yes" to a question, the flashlight flickers.

It turns out, there is a scientific explanation to why the flashlight flickers when he asks a question. Learning this, Dennis isn't disappointed. He is always a skeptic, though he won't ever let go of that experience.