Days after arriving, Foner was arrested for distributing leaflets in Canton, and almost arrested again while escorting ministers to a meeting. The first house hosting him was bombed, and the neighboring homes shot up. All across Mississippi, local and out-of-state civil rights workers, protesters, and people trying to register to vote were being arrested and attacked by mobs.

In one letter home, Foner described the events of a single day:

Two COFO volunteers were jailed on a trumped up rape charge. Forty M-1 rifles and a thousand rounds of ammunition were stolen from the local National Guard armory. As I write this letter, a Negro church is burning down the street; the fire department is nowhere to be found. Two other volunteers have just been arrested. Last night a Negro freedom worker was shot by white hoodlums. He was taken to the white University Hospital and was released about an hour later with the slug still in his head. Also last night Reverend Smith’s house was shot into about 1:30 AM by white men. The Negro guards fired back as the men got into a city truck.

At the end of summer, the volunteers — mostly white college students from the north — packed up and went home. The free schools and community centers had been a success, but only a few hundred people had managed to brave the intimidation and outsmarted the system to become registered voters. There was still work to do, and Foner stayed behind as a COFO project leader in Neshoba County. He was in the state when the interracial Mississippi Freedom Democratic Party challenged the mainstream delegation on TV at the Democratic National Convention in Atlantic City, when America heard Fannie Lou Hamer speak of her own failed attempts to register to vote, and of a near-fatal prison-cell beating she survived the year before. He was still there at the end of the year when the FBI arrested 21 men for the murders of Chaney, Goodman, and Schwerner.