Chapter 14 - "Percy and Padfoot" - In which Harry sends a letter to Sirius, he encounters Cho Chang and she calls him brave, and the Gryffindor team's first practice is less than spectacular. Percy sends Ron a letter warning him against continuing his friendship with Harry, and Sirius communicates with Harry through the common room fire.
In the Owlery
Early the next morning [Harry] awakens and walks down to the [common room] to write a letter to [Sirius] - which is challenging, since he must anticipate it being intercepted. He finally manages, though, and sets off to mail it.
[Harry] is stopped on his way to the [Owlery] by [Nearly Headless Nick], who warns him that [Peeves] is planning a practical joke further down the hall, so he heads a different way instead.
In the [Owlery], [Harry] mails his letter and is watching another [winged horse] over the [Forbidden Forest] when [Cho Chang] enters behind him. They chat for a bit, with her complimenting him for standing up to [Umbridge], when [Filch] arrives attempting to intercept Harry's letter. After Cho sticks up for Harry, they leave together, and Harry heads to breakfast.
An Awful Quidditch Practice
At breakfast [Harry] and [Ron] talk about [Quidditch], and [Hermione] learns from her [Daily Prophet] that [Sturgis Podmore] was arrested at the [Ministry of Magic]. The boys then decide to head out to the [Quidditch pitch] to practice together, despite [Hermione]'s clear disapproval.
[Harry] and [Ron] work on their [Quidditch] skills together, then head in for a quick lunch before coming out to practice with the entire [Quidditch team]. The practice doesn't go well, though, as the [Slytherins] show up to heckle and [Katie Bell] has to be taken to the [hospital wing] with a bloody nose.
[Harry] and [Ron] return to the [common room] to tell [Hermione] about their awful [Quidditch] practice, and then spend the rest of the weekend focused on homework, with only a touch of help from [Hermione].
[Hermes] arrives with a letter from [Percy], urging him to "sever ties" with [Harry] and outraging [Ron].
[Hermione] finally offers to correct [Harry] and [Ron]'s [Astronomy] essays, but as she does so [Harry] notices [Sirius]'s head in the fire. Sirius updates the three of them - saying he doesn't think [Umbridge] is a [Death Eater], that [Fudge] fears [Dumbledore] is training a private army of students, and that [Hagrid] is fine. But when he tries to offer to meet them in [Hogsmeade], [Harry] refuses, at which Sirius gets upset and disappears.
Chapter 15 - "The Hogwarts High Inquisitor" - In which Umbridge is made Hogwarts High Inquisitor, and Harry loses his temper again in Defense Against the Dark Arts, serving another week's detention. Umbridge observes the professors in class, and Ron and Hermione try to convince Harry to give Defence Against the Dark Arts lessons.