Cain was Adam and Eve's firstborn son. He was a tiller of the ground (someone who grows crops). Cain and his little brother Abel, each gave a gift to the Lord. Abel gave one of the firstborn of his flock and Cain gave some food that he grew. God liked Abel's gift better. Cain was so jealous that he killed Abel. When God asked Cain where his brother was, Cain was sassy to God and said, "I know not: Am I my brother's keeper?" God knew that Cain lied, so He punished Cain by making his crops never to grow again and by making him a wanderer (with no home) on the earth. Cain told God that his punishment was more than he could stand because people would try to kill him. So God said that anyone who killed Cain would be punished seven times as bad. God put a mark on Cain to protect him.