As they left the mansion, Sabu turned to Chacha and said, "Chacha, you're the best detective ever!"

Chacha smiled, puffing on his cigar. "It's all in a day's work, Sabu. Now, let's head back to the office. We have more cases to solve."

Sabu whispered to Chacha, "Chacha, I don't like this. It feels like we're being watched."

Chacha's eyes lit up. "Ah-ha! This is our first clue, Sabu."

The letter was from a wealthy businessman, Mr. Kumar, who owned a sprawling mansion on the outskirts of the city. He requested Chacha's presence at his mansion, stating that it was haunted by a ghost.