Charles shows up partway through Esmé and the narrator's conversation to deliver a message from Miss Megley – she wants Esmé to come back to their table and finish her tea.
Though he's supposedly "brilliant," Charles basically acts like a dopey, goofy little kid. He does some casual acrobatics under the table and tells the narrator that his eyes are orange (they're actually green).
Charles placidly blows a huge raspberry at the narrator.
Charles tells the narrator a riddle, and cracks himself up hysterically.
Moments later, Charles repeats the very same riddle, word for word.
The narrator doesn't give Charles a chance to get to the punch line, and answers the riddle before the little boy can. This is a total no-no.
Charles, seething with anger, flips out and leaves the table in a huff.
Esmé, Charles, and Miss Megley leave the tea shop.
Esmé marches Charles back in a moment later to give the narrator a kiss goodbye. He does so rather unhappily.
As Charles attempts to flee the scene, the narrator catches hold of his coat and pulls him back. The narrator asks Charles the riddle – Charles, incredibly pleased, delivers the answer and runs off, delighted.
Charles includes an adorable but uninformative note in Esmé's letter to Sergeant X.