The Paris Mysteries

Beginners. Speed Level 3 (70wpm) & 6 (100wpm). The room was on the fourth floor, and the door was locked-with the key on the inside. The windows were closed and the chimney was too narrow. How did the murderer escape? Whose were the two angry voices heard by the neighbour? Noboby in Paris could find any answers. Except Auguste Dupin.