SCOTTSDALE, Ariz. -- The father of a 22-year-old Scottsdale man who has been missing in Germany since Nov. 21 plans to fly there to help in the search.

• Watch: Missing Man's Dad Headed To Germany

Devon Hollahan was last seen at around 3 a.m. Nov. 21 after a concert in Frankfurt. He was traveling back to a hostel with a friend, who stopped to ask for directions. When the friend turned back around, Hollahan was gone.

Hollahan's father, Jeff Hollahan, said that hearing that his son had gone missing is "every parent's worst nightmare."

Jeff Hollahan said he plans to travel Sunday to Germany to help search for his son, who teaches English overseas.

"I've gone through every possible scenario and all of them make sense and none of them make sense," he said. "The worst case scenario is if somebody had killed him, we would have had a body."

Devon Hollahan had been teaching English in Prague since July.

"Every day there's more people involved, there's more support, there's more organization, there's more cooperation," Jeff Hollahan said. "Yet we're not closer today than we were a week ago."

Jeff Hollahan said he bought a one-way ticket to Germany. He said he won't be back until he's exhausted every effort to find his son.