Plagiarism

I had two plagiarized homework assignments last night. I knew students were not reading The Turn of the Screw as they needed to, even though I found them an audiobook to listen to online, which helped, many of them told me. I had many different exercises and discussed the books from a number of angles, comparing its ambiguity and open-ended structure to that of the other works we studied this semester, so it wasn't totally unfamiliar territory, but the students are tired, as am I. Tomorrow is the last day of class before they take the exam on Thursday.
The two plagiarized assignments obviously came from the same Cliff's Notes or Spark Notes. They discussed two sections of the book we had not touched on at all in ways that were totally foreign to our discussion of the book. I told the students that if they used such sources without citing them (and I didn't want them to use any sources but those I gave them), they were plagiarizing, and would get an instant F on the paper without a chance to rewrite it. I used to fail them for the whole class, but have since eased up on that.
The student came to me after class and said he felt discouraged because he had just failed the paper I just gave back too. He is a student capable of much better work, but sleeps during and skips class all the time, and rarely turns in homework. I didn't make nice to him. He deserves to feel discouraged. Maybe he'll figure out how he ended up in this situation and change his ways next time.