'For as in Adam all die, so also in Christ shall all be made alive.'
As a result of being 'in Adam' all men are dying. His sin and its taint carries through from generation to generation. All sin, and all are dying and will die. This is the due result of Adam's first sin, and of our connection with him. But in Christ a transformation has now taken place. Those who are in Christ, that is who have believed in Him, who have responded to Him, and who have come to Him through the cross, will all be made alive. He has received them and they are His. He was fully righteous in His life, and they have become righteous in Him with the righteousness of God (2 Corinthians 5:21). Having originally been affected by the sin of Adam believers have now been enveloped in the righteousness of Christ (1 Corinthians 1:30). This argument is expanded further in Romans 5:12 onwards. And in being enveloped in His righteousness they are borne along with Him towards the resurrection.