mysterypiece
nounUK /ˈmɪstəri piːs/
US /ˈmɪstəri piːs/
A mystery piece is a part of a puzzle or story that you have to figure out.
The detective found a mystery piece that helped solve the case.
OTHER MEANINGS
2. A small object whose purpose or origin is unknown.
In the attic, we found a mystery piece of old metal.
3. A part of a story or game that is kept secret until the end.
The last chapter revealed the mystery piece of the plot.
4. A missing part that makes something hard to understand.
Her explanation had a mystery piece that nobody could explain.