In the book of Exodus in the Bible, God told Moses to go back to Egypt to free the Israelites. He did and told the Pharaoh that if he didn't free them, God would do something about it.
God did, 10 times. Each act was a plague and in the end, the Pharoh relented. The plagues were:
  1. Water turning to blood
  2. Frogs
  3. Lice
  4. Flies - not where the Israelites lived
  5. Death of livestock - but not Israelite beasts
  6. Boils
  7. Hail storms
  8. Locusts
  9. Darkness - but not for the Israelites
  10. Death to all firstborn sons of both humans and cattle - except those who wiped the blood of lambs on both posts and the lintel of the door to the house they ate in.