Nate the Great has just recieved a strange musical note. The note tells Nate's friend Pip what his mother wants him to do at four o'clock. Their friend Rosamond, Pip's piano teacher, has turned the note into a riddle.
Nate the Great is on the case. He checks Rosamond's garage but doesn't find any clues. Later, Nate and his trusty dog Sludge don't see or hear anything strange at the band concert.
Time is ruuning out. It's almost four o'clock. Will Nate the Great stay stuck in the middle of this musical riddle?
大偵探奈特從朋友皮皮那裡收到了一張奇怪的五線譜紙條，上頭寫著媽媽要皮皮在下午四點做的事情。然而他們的好朋友、也是皮皮的鋼琴老師羅莎蒙，已經把這張紙條變成了一道謎題。
大偵探奈特接手了此案。他檢查了羅莎蒙的車庫，但卻沒找到任何線索。而奈特和他的好狗夥伴阿泥在接下來的樂團演唱會中也沒發現什麼異狀。
離下午四點一步步逼近，這張謎題會難倒大偵探奈特嗎？