1. Ms. Bluebird committed the murder in the closet with the telephone cord. (1)
2. Prof. Periwinkle killed the victim with the baseball bat in the den. (1)
3. Miss Crimson used the poison in the garage. (0)
4. Ms. Bluebird did it with the shotgun in the den. (1)
5. The murder was committed in the washroom or the foyer by Mr. Kelly. (0)
6. Sgt. Saffron did it with the telephone cord in the bedroom. (0)

Clues 3, 5, and 6 eliminate all of the rooms except the closet and the den. If the den is the murder location, Prof. Periwinkle and Ms. Bluebird are eliminated (clues 2 and 4). But this creates a problem with clue 1; Ms. Bluebird and the closet are eliminated, but the telephone cord was eliminated in clue 6. Therefore, the room cannot be the den. The room must be the closet.

If the closet is the room, clue 1 eliminates Ms. Bluebird. With Ms. Bluebird and the den eliminated, the shotgun must be the weapon (clue 4). Clue 2 leads us to Prof. Periwinkle as the murderer. Therefore, Prof. Periwinkle did it in the closet with the shotgun.