How many movies have Gabriele Niemeyer and Ralph Thiekötter collaborated on?

They have worked on 3 movies together! Their first movie together was The Three Investigators in The Secret of Skeleton Island (2007) while their highest rated movie together was The Three Investigators in The Secret of Terror Castle (2009). They have not worked together since The Three Investigators in The Secret of Terror Castle (2009). They are most known for their mystery films together.