In part 3 of the story why do you think that Scratch agrees to the trial at this point?

By this point in the story, Jabez Stone is starting to realize that he made a bad deal when he agreed to sell his soul to the devil. But a deal is a deal, says Scratch, and so poor old Jabez Stone will just have to like it or lump it. Stone doesn't give up, however, and does what many people do when they want to get out of a bad contract: he hires a lawyer to argue his case. And it's not just any lawyer, but none other than Daniel Webster, Senator from New Hampshire and the best attorney in the country.
Webster approaches Scratch and insists on a trial. Scratch agrees, but only on condition that Webster will forfeit his own soul to the devil if he loses the case. Taking control of any man's soul is a coveted prize for the Prince of Darkness, but to have in his possession the soul of such an important man as Webster is beyond his wildest dreams. So he figures that if the trial goes ahead—especially if it's presided over by the judge at the Salem witch trials and with a rigged jury of disreputable characters like Benedict Arnold—then he's sure to get his Satanic claws round the soul of one of America's most admired men.