Cache

cache
noun. A collection of items of the same type stored in a hidden or inaccessible place. A hidden or inaccessible storage place for valuables, provisions or ammunition. "Cache memory" in computing: An auxiliary memory from which high-speed retrieval is possible.
verb, transitive. To store away in hiding or for future use.

Raising the lantern to illuminate it, she gestured toward the brick wall with her free hand.
"The cache is behind there," she told Lee. "The brick's only a veneer."

Lee took his hands out of his pockets and rubbed them on his hips. "So, how do we get into it?"

Instead of replying, she placed the lantern on the packed-earth floor and walked to the wall. Starting at the ceiling, she counted bricks downward, then counted two from the left. With the blade of a pocketknife, she pried at the lower edge of the brick her count had stopped on until it swiveled upward. She reached into a recess behind it and turned a handle Lee could not see.

She braced herself and pulled. The seemingly-solid wall opened like a door. She propped it wide with a real brick, then picked up the lantern so she could shine its light on what lay behind the cache door: an array of assault rifles and boxes of ammunition.

Definitions adapted from The New Oxford American Dictionary, Oxford University Press, Inc., 2005 (eBook Edition, copyright 2008), and from Webster's Seventh New Collegiate Dictionary, G. & C. Merriam Company, Publishers, Springfield, Massachusetts, USA, 1965, depending on which is more convenient to hand.