I believe the answer is "The girl who owns a red car is the one we are looking for."
The restrictive clause is "who owns a red car". That clause describes the girl.
Answer:
Charlie trudged through the mud. His feet were as heavy as cinderblocks as he tried to pull them up through the mud. He began to panic as his feet stuck in the mud and slowly started to sink. A boom as loud as thunder sounded from behind him. Whipping his head around, he saw a figure as dark as the night around him. The fog seemed to blanket the cloak the figure was wearing. Charlie tried to scream but his mouth was as dry as chalk. The last thing Charlie saw was the figure swoop down on him before he woke up in a cold sweat. It was simply a bad dream!
Explanation: