Eldon's love letter is printed on regular lined noted paper. Although it is never read aloud in its entirety, it is presumed to be extremely romantic and heart-felt. Two of the lines that are revealed (loosely) describe how Eldon "gets lost in the hazelnut pools of Thalia's eyes" and "sees invisible bolts of lightning shoot off of her body when she dances."
Although the letter is intended for Thalia's eyes only, Michelle is first to find it and read it; thankfully, the letter is addressed to Thalia, so there is no confusion. Finding it endlessly romantic, Michelle searches for Thalia so that she can give her the letter and ends up in Hidalgo's. James finds her there and takes the letter from her after realizing what it is (as it is a violation of Eldon and James's agreement that Eldon will not date or merely communicate with Thalia until he reaches 30 pirouettes).
James, now owning the letter, bequests the arrival of Thalia and Eldon. When they arrive, James voices how irate he is with the violation, and angrily reads the two aforementioned lines of the letter. Although Thalia finds it romantic, James decrees that the two can now no longer talk on any terms. He crumples up the letter and orders the two to leave.