So it’s Christ’s FINISHED WORK PLUS baptism ? Then His work was not FINISHED, if there remained something else to be done by US. What if a person is on their way to the Church to be baptized and suddenly suffers a fatal heart attack before he can be baptized?
Try looking up baptism be desire.
The atonement itself does not convert a person, but rather than heart-purifying faith being counted for righteousness, and thus the believer being accepted in the Beloved on His account and spiritually made to sit together with Him in Heaven, with immediate access into the holy of holies to meet with God, (Rm. 4:5; Eph. 1:6; 2:6; Heb. 10:19) so that all believers immediately go to be with the Lord at death or His return . (Phil 1:23; 2Cor. 5:8 [“we”]; Heb, 12:22,23; 1Cor. 15:51ff'; 1Thess. 4:17) And with the the only suffering after this life being that of the loss of rewards (and the Lord's revelation and disapproval) at the judgment seat of Christ, which one is saved despite the loss of, and which does not occur until the Lord's return and believers resurrection; (1Cor. 3:8ff; 4:5; 2Tim. 4:1,8; Rev.11:18; Mt. 25:31-46; 1Pt. 1:7; 5:4)
RC teaching is that baptism works "ex opere operato" - by the act itself/by virtue of the action - then the subject is regenerated - even if morally incognizant and thus incapable of the Biblical requirement of wholehearted repentant faith (Acts 2:38; 8:36,37)- though the baptizer (even a Prot) must have the proper basic intention of doing what the Church does, and form and matter, and the subject normally must have a proper disposition (and since one cannot know the hear of the minster, the recipient may doubt if the sacrament is real). In Rc teaching, anyone can baptize, but in general other Sacraments need a Bishop or a Priest.
And that this act thus renders the subject good enough to enter Heaven - formally justified by his own (infused) righteousness.
However, since his unholy sinful nature is all too alive and well, and is soon expressed, then unless he/she is one of the few to attain to the level of holiness of heart and character needed to see God in Heaven, then it is imagined that one (most all) much ensure purifying torments in mythical RC (the EOs tend to have a different version) Purgatory. See here for some documentation and further explanation, by the grace of God.
What if a person is on their way to the Church to be baptized and suddenly suffers a fatal heart attack before he can be baptized?
In such a case there is the contentious (some TradCaths reject it) teaching of "baptism by desire" in which the desire is counted for the act.
Rome allows for salvation without baptism through perfect contrition (contritio caritate perfecta, which, works ex opere operantis: Catholic Encyclopedia>Sanctifying Grace; http://www.ewtn.com/library/DOCTRINE/BAPTISM.TXT)