K.P. Yohannan explores the theme of human failure and divine restoration in the sermon 'After the Fall.' He illustrates how figures like Abraham and Samson, despite their significant flaws and failures, were still used by God to fulfill His grand design. Abraham's journey of faith was marred by deception and impatience, yet he became the father of many nations. Similarly, Samson's moral failures did not thwart God's purpose, as he ultimately achieved greater victories after his restoration. The sermon emphasizes that God's plans prevail despite human shortcomings.