There was once a bachur in the Ponivitch Yeshiva who was considered a very good, serious boy. That was on the outside. On the inside - he was rotten....
He had the following custom: He would go to one Rosh Yeshiva, Rav Shach, and hear a good question. Then he would go to a different Rosh Yeshiva, Rav Shmuel Rozovsky, and ask the question as if he thought of it himself. Rav Shmuel would give him a detailed and profound answer to the question. He would then return to Rav Shach with "his" explanations. Rav Shach would debate the points he made with his famous powers of analysis. He would then return to Rav Shmuel with "his" analysis of Rav Shmuel's answer and so on and so forth.
He seemd to the Rabbonim like a really SHTARK boy. He mamesh was learning on the level of the Roshei Yeshiva themselves.... And he wasn't yet 20 years old!!
One time he was talking in learning near Rav Ben Tzion Felman ztz"l, a talmid of the Chazon Ish and later a famous Rov in Bnei Brak. Rav Felman never noticed or related to what was going on around him as he was too immersed in his learning. But this time he said to his chavrusa "מסריח פה" - it smells really bad here. And he moved places to distance himself from this boy.
This boy later became a virulently anti-religious journalist who was excommunicated by his family...
As a footnote, soon before he died he was in a car accident and had a NDE [near death experience] where he detailed and described how he met up with his late father. The people who were the first to resuscitate him were the Charedim he so despised. But that didn't spur him on to teshuva either. He died soon after and his family was told by one of the Gedolei Hador not to sit shiva for him.
Lesson: Torah without Yiras Shomayim isn't Torah.
