Yesterday I mentioned that Apollos probably knew only about John the Baptist and not about Jesus. We catch a glimpse of more such people at Ephesus in Acts 19.
In fact, there may have been followers of JB at Ephesus in the late first century who actually rejected Jesus as the one to whom JB pointed. If the Gospel of John was written at Ephesus, could this be why John's Gospel seems to downplay JB (it never tells about Jesus being baptized by JB, JB does not admit to being Elijah, Jesus' disciples baptize at the same time as JB)?
In the incident between Paul and a dozen followers of JB at Ephesus, they have not heard about the Holy Spirit. As Priscilla and Aquila did with Apollos, Paul presents Jesus to them and gives them the rest of the story. They are baptized again in the name of Jesus. They receive the Spirit. They even speak in tongues and prophecy.
I think the point of telling this story might be to make it clear that the baptism of John the Baptist is not enough. It is baptism in the name of Jesus that is the baptism that relates to salvation. It is a baptism that leads to receiving the Spirit, and the tongues speaking authenticated it. (no indication is given that everyone will speak in tongues or whether these tongues were other languages, as in Acts 2).
This is thus not an argument for re-baptism of adults who were baptized as children. From a Christian perspective, this is the first baptism of this group. Again, calling the Jesus movement "the Way," we remember that JB preached, "the way of the Lord" and that John, perhaps written to the Ephesus community, calls Jesus "the way, the truth, and the life."