It is summer and the Tiger Team longs for new cases to solve and mysteries to unravel. When Bigi, Luk and Patrick lay hands on a cryptic object, they know a new adventure lies ahead. Their research uncovers a connection to China. Could the object be one of the three keys that will open the doors of the Moonlight Palace in the Mountain of 1,000 Dragons near Beijing? The only way to find out is to go there… As soon as the Tiger Team reaches China, Bigi is attacked and the key is stolen. The elderly Cheng, who originally had sent the key to Europe to keep it safe, offers to help the three friends. He fears that the ancient key has been snatched by the notorious Lady Q, the head of the secret order of the Black Snake. In fact, Lady Q and her henchmen kidnap Cheng and mercilessly pursue the Tiger Team through Beijing in search of two more missing keys and the secret map. Although the palace conceals unimaginable treasures, all that Lady Q really wants is the elixir of immortality that would make her invincible. According to an ancient legend, this elixir was given to a boy emperor 600 years ago. In order to free Cheng, the Tiger Team is forced to help Lady Q. As one key after the other leads to new and frightening dangers, the group finally makes it into the furthest recesses of the mountain palace – where they meet the boy emperor himself…