The Onyx Plate needs to be combined with the goddess statue located in the Main hall, after removing the Unicorn Medal. Once all five plates have been placed, a secret passageway underneath the statue opens, enabling the female officer Rita to squeeze inside a narrow tunnel to get to the other side and call for help.
The Onyx Plate is located in different places according to the difficulty:
- Inside Marvin's cubicle in the east office. Read the Police File in the Reception Room first, then enter the combination in the safe.
- Inside the Kennel. Unlock or break down the locked door leading to the room.