Warehouse Key is a written note found in Dishonored 2.
It's done, Reid finally gave in! She'll drop the warehouse key where we told her, behind some bottles.
Don't forget, use her name. You're Miss Fenella Reid, and you're the Boyle Company Import Manager.
Once you've greeted our businessman friend from Morley at the docks, open the warehouse for his crew so they can unload the goods. I'll start transferring them to the shop through the ceiling as soon as they're done.
In the meantime bring the Morleyan to the Boyle offices. Pretend that everybody is on holiday for some reason, still mourning the boss maybe. Make him sign some papers, use whatever forms you can find there, and make sure to stamp everything with conviction.
Give him a Cullero cigar from the reserve, anything to make him trust you. And remember to wear something clean.
Everything's got to be finished up before sunrise.
It can be found under the door to the locked warehouse beneath the Black Pony Pub in the mission Death to the Empress.