The unexplained mystery surrounding the disappearance of the hiker baffled investigators.
The unexplained phenomenon of the lights in the sky sparked a debate among the townspeople.
The unexplained anomaly in the data set raised doubts about the accuracy of the results.
The unexplained occurrence of strange noises in the old house kept the residents on edge.
The unexplained puzzle of how the ancient structure was built still perplexes archaeologists.