This case study investigates the effectiveness of a lecture in advanced mathematics. We video recorded a lecture delivered by an experienced professor. Using video recall, we then interviewed the professor to determine the content he intended to convey and we analyzed his lecture to see if and how this content was conveyed. We also interviewed six students to see what they understood from this lecture. The students did not comprehend much of the content that the professor intended to cover in his lecture. We propose three reasons for why students failed to grasp much of the content that the professor intended to convey. [For the complete proceedings, see ED597799.]