What arrangement does Walker finally make with the stranger, and what does Walker do when he begins to regret making this decision?

In Part II, Tom decides he will agree to anything so long as he receives the treasure. He goes to find Old Scratch, and they haggle about business; Old Scratch insists that money found through his means should be employed in his service. First he wants Tom to build a slave ship, but Tom refuses to be a slave trader; his conscience could not handle it.

Tom proposes instead that he become a usurer and extort bonds and foreclose properties by lending money with far too high an interest rate. Old Scratch agrees to this, and Tom sets up right away as a usurer in Boston.