The four-word code was a crucial clue that helped solve the mystery of the missing stolen jewellery. Nolan used the names of days of the week, dropping the letters d-a-y, to form four code words that pointed toward the hiding place of the loot. This clever use of language and codes required critical thinking to decode. It led Encyclopedia to discover that the jewellery was hidden inside a jug of earth where a young fir tree was growing, fulfilling the clue of the unwritten fifth word, “Fir.”