The episode begins with three Noh masks museum employees conspiring to murder the museum curator. Detective Mouri, Ran and Conan show up at the museum explaining that they received a letter warning them that the museum curator's life is in danger. They meet the museum curator, his personal nurse, and his businessman acquaintance in the garden. Soon a heavy pile of logs roll out of the shed and almost crush the group. Other "accidents" occur until the businessman is poisoned and dies.