Describing something as intricate, convoluted, and strangely mysterious; a four-character idiom used often in written contexts.
その事件の背景は複雑怪奇で、捜査は難航している。
The background of that case is convoluted and bizarre, and the investigation is struggling.
小説の筋は複雑怪奇だが、読み応えがある。
The novel's plot is intricate and strange, but it's rewarding to read.
彼の説明は複雑怪奇で、結局何を言いたいのかわからなかった。
His explanation was convoluted and strange, and in the end I couldn't tell what he meant.