Dd(14) told us she was at an event when she was actually at her boyfriends house. I'm pretty sure she did it because she had been grounded for the week before but we lifted it so that she could go to the event. Had she told us the truth she must have thought we would say no. But it was her best friends Mum who told me where she was as she overheard her daughter and friend talking about it. They begged her not to tell me. How can I tell dd I know without dropping them in it?