One thing leads to another British American sentence informal
One event or action causes others that are unplanned or unforeseen.
My father bought a car, then a house, and then a boat. One thing leads to another.
We went to meet for coffee, but one thing led to another, and now we've married.
I lent her a pencil, and one thing led to another until I ended up helping her color the whole picture.
The verb "lead" should be conjugated according to its tense.
Unknown origin
Used to refer to a person who is your enemy
He faced his sworn enemy.