You need time to find the key. The footsteps stop outside your door and muffled voices can be heard. At least they are locked out too.
SHATTER! Goes the glass in the window, they are using a fire axe to enter! You find the right key just as an arm reaches through the shards in the portal and begins fumbling for the lock. Opening the water closet door you dart inside and lock it behind you leaving the key in the lock so no one can enter.
With relief you sigh and step on the hand of the... He's awake! He grips your foot, lifts it high in the air and throws you off balance. Your head falls on the tub snapping your neck. He pulls the golden chain and the attached prize of the Amulet of Future Knowledge from it and unlocks the door.
"Oh! What tragedy. Master must have slipped on the soap. I found the body like this when I came in to tidy up. He seems to have broken his neck and is quite dead. I'll go report this to the captain." he lies to aunt Marion and Salah as he slips out the door and down the stairs. He thinks "What a coward." as he dives into the water to swim to the waiting yacht.