In the beginning of the story, the people of the village were gathering like it says on lines 3-5, "the people of the village began to gather in the square, between the post office and the bank, around ten o'clock". This made it a mystery because we didn't know what they were gathering for.
On lines 156-157 Mr. Summers gave instructions saying, "keep the paper folded in your hand without looking at it until has had a turn. Everything clear?" People seemed nervous once he was done, "most of them were quiet, wetting their lips not looking around". As said on lines 160-161. This created tension in this part of the story.
A surprise at the end of the story is when In the end of the story, Tessie is stoned to death. This is because she has picked the piece of paper with the black mark..