The Dinner at Mayor's House was a dinner made by Hart Thorin to introduce his guests from the In-World, the three supposed counters sent by the Affiliation: Will Dearborn, Arthur Heath and Richard Stockworth.
The dinner occurred three days after the three boys came to Hambry, and it was there that "Will" met Herkimer Avery and Hart Thorin.
This also is where Roland finds out that Susan Delgado is Hart Thorin's gilly. When he sees Thorin standing near Susan Roland assumes that he is Susan's cousin or uncle. Later while everyone is having dinner he ask if the mayor is related to Susan. This is met with laughter at his side of the table and is then told by Coral Thorin that she is his gilly. This realization was shown to anger Roland. later at the dinner when everyone began to dance Roland got paired up with Susan, and out of anger and a little disgust he insulted her intelligence by acting surprised that she knew the word propriety.