A strange old man drops in Mouri. He is actually Mouri's teacher, who was a famous detective. Conan can't wait to see the reasoning progress of him. So Ran and Conan lead him to the theater.
There, Mouri is doing with a threatening letter, in which says the actress will be killed. During the rehearsal, after eating the fake poison and drinking a glass of water, the actress pretends to be dead. However, when the rehearsal ended, the director couldn't wake up the actress, she is really dead.
Inspector Megure comes, he is also the apprentice of the old man. Conan doubted about the salacious old man. He asks him whether he knows the murder. And he replies that the murder is a woman for the simple reason that behind every murder case, there is a woman. Conan really feels disappointed about the legendary famous detective.
The old detective also tells Conan something about cobweb. Conan does not understand why he say such unrelated things. But when he notices the stars suspended from the ceiling, he suddenly recognises something. He climbs up to the ceiling. Just above the glass the actress used, the star is enlaced by a thread.
Now Conan understands. The murder imbrued the poison on the star, and suspended a thread with a clog from the star. By prolonging the thread to another place, she can control it everywhere. When the glass is placed at the pre-arranged point, she let the thread down into the glass, and the poison on the star may go along the thread, till into the glass. Then she pulls the thread back. But because of nervousness, she over-tugged and snapped the thread, thus why the star is intertwined by thread.
Conan finds the hand of a workwoman has the sign of thread. So she is the murder. Since Mouri is not here for some reason. Conan decides to take his teacher for instead. Everything goes on well, problem settled.
When wake up, the old man receives praise from people, which makes him very happy. Conan thinks Mouri's bad habit of impudence must comes from his teacher. What's more, there are many things they have in common. They all have nothing to deal with women.