Mysterious: /mɪˈstɪərɪəs/ difficult or impossible to understand, explain, or identify. “his colleague had vanished in mysterious circumstances”.
Hypotheses: /hʌɪˈpɒθɪsɪs/ a supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation. “his ‘steady state’ hypothesis of the origin of the universe”.
Unsolved: /ˌʌnˈsɒlvd/ not having been solved. “an unsolved murder”.
Coincidence /kəʊˈɪnsɪd(ə)ns/ a remarkable concurrence of events or circumstances without apparent causal connection. “it was a coincidence that she was wearing a jersey like Laura’s”.
Adventure /ədˈvɛntʃə/ an unusual and exciting or daring experience. “her recent adventures in Italy”.
