adj. 25B6; adjective
he vanished in mysterious circumstances : PUZZLING, strange, peculiar, curious, funny, queer, odd, weird, bizarre, mystifying, inexplicable, baffling, perplexing, incomprehensible, unexplainable, unfathomable.
he was being very mysterious : ENIGMATIC, inscrutable, secretive, reticent, evasive, furtive, surreptitious.
straightforward.