C1122 This is really unexpected

Long Tianci and the rest all stared curiously at Cao Youyi who was knocking on the door. This fellow's tapping rhythm was very special, it would take at least two to three times, and it was very obvious that this knocking sound was a secret signal. When the people inside the door hear the signal, they would open the door, if not, they would not even knock on the door until it was broken