After the incident in the store at Strawberry in which the assertive Cassie objects when the storekeeper Mr. Barnett waits on white people ahead of her, and she has to apologize to Lillian Jean, tensions begin to mount.  Uncle Hammer, who is visiting, learns of the incident and angrily jumps into his car with Mr. Morrison accompanying him. In another incident, Uncle Hammer forces a white man in a truck to back off the bridge so that he can drive across.  As the white man tips his hat, he realizes that he has made this gesture to a black man. Mama tells Hammer that he should not have forced the white man back,

"But one day we'll have to pay for it.  Believe me..."

Then, in Chapter 7 of Roll of Thunder, Hear My Cry, Big Ma, who knows of all the incidents that have occurred, has talked to Mr. Jamison, the lawyer whose office is in Strawberry. Big Ma has summoned Mr. Jamison so that she can be sure that nothing will happen to the property when she is gone; that is, she wants to assure herself that Harlan Granger will not be able to attain her property on a technicality after her death. 

Mr. Jamison warns the Logans against using their land as collateral to back credit for black sharecroppers at the store in Vicksburg because Harlan Granger will seize any opportunity he has to take away their property.  But, then, he offers to back the credit himself.