The Serpent, who is the devil and Satan, deceived Eve and Adam, who knew better, ate from the forbidden fruit. Death entered their soul, and separation occurred between God and them. Life left them, and darkness filled the void. They knew they were naked revealing sin in their minds.
Many sinful thoughts for the first time permeated their minds and caused them to die spiritually, and in a gradual state, physically.
The good news is that Jesus Christ brought life to those who accept Him as Lord and Savior. Jesus paid in full on the cross, our doubt of sin. All we need to do and ask Jesus to forgive us and save us from our sins.