Working from the 1970s to the early 1990s, Walter Alvarez and his research team sought the cause of the mass extinction that claimed the dinosaurs 65 million years ago. The present paper discusses that research in terms of eight puzzling observations, eight episodes of hypothetico-predictive reasoning, enumerative induction, and Jung's interrogative theory of scientific discovery. The Alvarez case history paints scientific discovery as a process in which causal questions are raised and answered through the creative use of analogical reasoning followed by an equally creative process of hypothesis testing in which predicted and observed results are compared. According to this account, puzzling observations, causal hypotheses, and imagined tests drive investigations and the search for evidence. Two implications follow. The first concerns the education of new scientists and science education researchers and the need to more clearly differentiate hypotheses from predictions in the research process. The second concerns standard science classroom instruction that should more frequently engage students in open inquiries that raise causal questions and encourage the generation of alternative causal hypotheses, which can then be explicitly tested in a hypothetico-predictive fashion.