Paycheck by Philip K. Dick

A skilled engineer agrees to have years of his memory erased in return for a large payment after working on a top-secret project; when his contract ends he is left only with a sealed envelope of seemingly trivial everyday objects and a cryptic instruction to open it later. As he is hunted by powerful interests and faces a cascade of threats, he discovers the items were deliberately chosen—using his own foreknowledge during the erased period—as a set of tools and clues that enable him to outwit pursuers, unravel a conspiracy, and regain control of his fate.

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