Typically - a "baptism" scene in literature would be like any major moment of conversion - hopefully an experience that results in a better version of the character.
One such experience is in Victor Hugo's Les Miserables. The story opens with Jean Valjean - an ex convict who has just been released from 19 years in jail. He cannot find an inn to serve him any food, let alone give him a place to stay - because of the "convict" stamp on his papers. Finally, he is let into the house of a bishop - who not only serves him dinner, but gives him a bed - and treats him like a man. That night, Valjean robs the bishop of some silver plates. He is caught down the road and brought back to the bishops house - to face the man whom he robbed - the first man who looked into Valjean's eyes and treated him as an equal. Instead of confirming that he had been robbed, the bishop demonstrated one of the greatest acts of mercy in literature. He said to the policeman that the silver belonged to Valjean - it was a gift, and to prove it, he got out two silver candlesticks and said, basically, here, you forgot these. The bishop handed Valjean his freedom in one major act of forgiveness. As the police leave - Valjean is so full of shame that he cannot even meet eyes with the Bishop. At this moment, the Bishop says, "Remember this brother - use it to become an honest man." (Loose quote.)
This is the moment of Valjean's transformation. He does indeed become honest as a result. The events of the book from this moment on - show Valjean as a humanitarian, a giver, compassionate, SELFLESS. As a result of his conversion - he shows mercy to countless others and perpetuates the cycle - just after his own baptism, Jesus' ministry really takes off.
"Intertextuality" - is when the meaning of a text is largely shaped by the knowledge of other texts. The most prominent example of "intertextuality" in literature is the use of Biblical parallels and allusions. Consider how many novels have a "Christ-figure" in them - a character who seems to sacrifice himself time and again for the betterment of someone else. Think about books like The Scarlet Letter which are largely built around religious themes. They are prominent in American literature because so much of America's historical foundation was built around the church.