>> lopera: at 51. >> stahl: oh! dr.ra was convinced that what he and madrigal were discovering was scientifically important, but even as they found more patients and more related families, he couldn't get anyone outside colombia to take notice. until 1993, when a harvard professor came to give a talk about alzheimer's in bogota, several hours away. >> ken kosik: there was a person in the audience, francisco lopera, who came up after the talk and said, "you know, there's-- i have a family here that w-- has-- early-onset alzheimer's." >> stahl: ken kosik, now at u.c. santa barbara, was that professor. a family. could've been four people. >> kosik: it could've been just four people. but he started to tell me how many it was. and as i listened to him, i became just so absorbed and taken with what he was telling me that i changed all my plans, went with him to medelliiÍn. and-- we began a collaboration that goes on to this day. >> stahl: they showed kosik what lucia madrigal showed us-- the family tree they had compiled, bas