From Section II, we infer that Farquhar, almost literally the only character, was lured or even entrapped into an attempt to blow up Owl Creek Bridge. Which event foreshadowed that Farquhar was being lured or entrapped?

In part II of the story, the narrator describes a recent evening when a "gray-clad soldier" rode up to the Farquhars' home. Confederate soldiers wore gray uniforms during the Civil War, while Union soldiers wore navy blue; thus, Farquhar assumes that the man he is speaking to is a fellow supporter of the Confederacy and fights for the south. When Farquhar requests news of the front, the soldier informs him that the Northern soldiers are repairing the railroads, transportation lines which are vital to their war effort. The soldier mentions the Owl Creek Bridge, some thirty miles away from Farquhar's home, and he describes the scarcity of its guards. Farquhar then asks,

Suppose a man [...] should elude the picket post and perhaps get the better of the sentinel, [...] what could he accomplish?

He wants to know what harm he could do to the Union effort. We can imagine, then, that he will take the soldier's hint to set fire to the bridge in order to disrupt the Union war efforts. Finally, after the soldier drinks the water brought to him by Mrs. Farquhar, he takes his leave. The narrator, in the final sentence of part II, informs us that the soldier "was a Federal scout." In other words, he is not a Confederate soldier but works for the Union army. In this way, he lures Farquhar into committing the crime for which he is hanged.