His true motives remain a riddle wrapped in an enigma.
riddle wrapped in an enigma
idiomSomething very mysterious and hidden.
Origin
first recorded 20th c.A variation of Winston Churchill's quotation, made in a radio broadcast in October 1939.
The politician's sudden change of heart is a riddle wrapped in an enigma that confuses his closest supporters.
The ancient manuscript, filled with cryptic symbols and contradictory historical accounts, remains a riddle wrapped in an enigma for modern scholars.