From Longman Dictionary of Contemporary Englishthe next thing I/she etc knewthe next thing I/she etc knewinformal used when something surprising happens very suddenly The next thing I knew, I was lying face down on the pavement. → next
Examples from the Corpus
the next thing I/she etc knew• I had hardly dated, and the next thing I knew I was getting married.• And the next thing I knew, I was here.• I started to run and the next thing I knew I was lying on the kitchen table.• I must have fallen asleep, for the next thing I knew I was woken by the ringing of the telephone.• But the next thing she knew she was crying.• I fell asleep, and the next thing I knew, some one was waking me.• He slipped something in my wine and the next thing I knew was that we were on the Continent. 