Enter the Old Clockworks at 3:30
Open the Clockworks Court barrier with the Strobulb. On the right, stun the Robomb so its explosion clears the scrap blocking the rail. At the rail’s end, restore the hidden toolbox for the first ruby. Set the entrance clock to 3:30: hour hand on three, minute hand on six. Enter the Warehouse. Restore the hidden green ribbon spool, put it in the machine and unravel it for a ruby. A red spool contains the mission’s Boo; the safe’s spool provides the key for the Workshop.
Open the way above the Cargo Room
Use the Workshop’s Robomb to expose the ghosts, then clear the room and enter the Clock Tower Gate. The main clock is missing its hands. Defeat the ghosts that appear when you inspect it and take their key. Restore the hidden toolbox in the back-left corner for another ruby. Continue into the Cargo Room, uncover and activate the Robomb to release sand, then pull the hanging cord to expose the stairs. Clear the ghosts on the upper route before using the higher door.
Recover the compass in the Drafting Office
Use Dark-Light to restore the missing upper bridge at the Clock Tower Gate. In the Drafting Office, clear the paper-carrying Greenie and turn the ceiling fan to rotate the partitions. Search the newly exposed workspace and catch its ghosts, including the Sneakers. Once the room is clear, inspect the desk drawer for the compass. This compass opens the underground entrance in C-2; it is not one of the clock hands.
Collectible checklist
Old Clockworks gems — #1 Clockworks Court, #2 Warehouse, #3 Clock Tower Gate
Boo checklist — Warehouse: Put the red ribbon spool from the right side in the machine and unravel it. The hidden green spool contains a ruby instead.