This is probably the best episode of the season.
The gang enters rural Ohio, where a mysterious man walks in front of the bus. Ned doesn't see him in time and runs right over him - but we see that the man is not affected at all and the bus goes right through him like he's not even there. The sudden appearance causes a frightened Ned to swerve and crash the bus into nearby yard, demolishing the picket fence.
The owners of the house - Seth, and his beautiful daughter Gabe, rush out, making sure they are ok. Molly apolozizes and assures him the damage will be paid for. Seth tells them the only important thing is that they are ok. Fi notices Jack and Gabe's sudden chemistry, and notices her and her father's reaction when Ned tells them he thought he saw a man in the road.
Irene's cell phone has mysteriously stopped working, so Seth offers them residence in their home for the night. Molly finally accepts the offer.
Fi later confronts Gabe about the man Ned saw in the road, and discovers Gabe believes him to be her guardian angel. However, after a frigtening encounter with the man that night, Fi comes to believe the man is some sort of demon. She later learns from a mechanic that over five cars have broken down in front of Gabe and Seth's house in less than three months.
Fi is later visited again by the mysterious being, and he shows her her bones. Fi is scared, and tells Jack there is something trying to hurt Gabe. She and Jack go up to Gabe's room, and Fi sees a bright light and the man. She realizes he is an angel, and follows him into the light. From Jack and Gabe's point of view, Fi is just walking across her room.
The angel shows Fi different scences from Gabe's recent life, and she realizes that she has leukemia. Fi wakes up in Gabe's living room, on the couch, surrounded by everyone. She tells Gabe that she is a match for her bone marrow transplant. Gabe and Seth are mystified: they didn't tell anyone she had cancer.
Later, at the hospital, Fi comes out of the OR, having given her bone marrow. She gives Jack Gabe's angel necklace, telling him she wanted him to have it.
This was an amazing episode. The effects were cool, the storytelling was cool. It was just cool.