The pattern is always the same: Two minor, innocuous incidents, and then the whammy: "...and the next thing I knew, we were having sex." The most popular way to brag, to confess to someone you've cheated on, or to answer an angry parent who has asked, "How did this happen?", as a way to avoid going into all the details no one really wants to know. If this is how someone (optimistically) plans to get someone into bed, it's Step Three: Profit - Step One, Boy Meets Girl; Step Two: ???; Step Three: Coitus Ensues! Don't Try This At Home. Examples of One Thing Led to Another include: