A WIFE LEARNS OF HER HUSBAND�S ULTIMATE BETRAYAL AFTER A DECADE OF MARRIAGE � AFFAIRS WERE ONLY THE BEGINNING FOR THIS REAL LIFE DESPERATE HOUSEWIFE � ON �PRIMETIME,� THURSDAY, JANUARY 12 AT 10:00 P.M., ET

Also: �Primetime� Examines Why People Follow the Pack

Cheri Kostrewa thought she knew her husband Harald Ehrenfelds well. They had a happy life and loving marriage. But after nearly a decade and the birth of their first child, Kostrewa says she began to notice changes in her husband�s behavior. He would refuse to eat, was increasingly removed from the family, and started ignoring her. She was concerned for the person she that she had once been inseparable with. Yet it wasn�t until 14 years into the marriage that Cheri�s devastation truly set in when suspicious letters started arriving from another woman in Norway � a woman who had been Harald�s first love. While she wouldn�t be the only other woman, Cheri had even bigger concerns. After their second son, Erik, was born, Cheri started to fear for her own safety. From a vile tasting glass of water that sat next to her bed to a mysterious green powder that kept appearing in her food � could it be that her own husband was trying to poison her? Cynthia McFadden reports on �Primetime,� airing THURSDAY, JANUARY 12 (10:00�11:00 p.m., ET) on the ABC Television Network.

Also: The debut of a new �Primetime� feature: Primetime Labs, which will focus on human nature and behavior. First up -- we all do it -- we follow the leader and take our cues from the crowd. From fashion to pop culture to politics, we tend to conform to the group. But have you ever wondered why? �Primetime� did � and with the help of ground-breaking researcher Dr. Gregory Berns of Emory University, performed our own demonstration - gathering one group for a seemingly simple visual test and another group for a dinner party with a sociological twist. The results are astounding. So why do people exhibit this fascinating behavior time and time again? Dr. Berns explains how this may be all in our heads.

DIANE SAWYER, CHRIS CUOMO, CYNTHIA McFADDEN and JOHN QUINONES are the anchors of �Primetime.� DAVID SLOAN is the executive producer.