Haunting surveillance video is at the center of an agonizing mystery.
Teighlor Stegman is her best friend. Stegman told a reporter, "We found her car a few days later, parked over here. It was untouched, didn't look like anybody had been inside of it."
Christina's father reported her missing. He said, "You run though scenarios in your head. You try to figure out where she's at. We just want to bring her home."
Everyday, Christina's mom writes messages to her missing daughter on Facebook, such as, "Please keep staying strong with me, sweetie. We are getting closer."
So, who was the guy in the video walking with Christina?
Cops identified him as Enrique Arochi, a friend of Christina's from high school. He told police that he and Christina had been at the party together but went their separate ways in the parking garage, and that he knows nothing about her disappearance.
Arochi told WFAA-TV, "I feel like they were wasting their time on me when they could be looking at somebody else that is actually the suspect or the person that actually did it."
But not long after Arochi gave this interview to the station, police arrested him for kidnapping, after allegedly finding Christina's DNA in the trunk of his Chevy Camaro.
He also allegedly had "a bite mark" and "abrasions."
It is now four weeks after Arochi's arrest and there is still no trace of Christina, or her body.
Volunteers scour the area every day, whatever the weather. Even drones have been used.
Now, Christina's mother has this message to the suspect: "Enough is enough. You've put me through pain. You've put Christina through pain. You've put your family through pain. Please dig deep down in your heart and give us the answers to lead us to Christina. We need her home."