Hans Urs von Balthasar (1905-1988) was one of the most prominent Roman Catholic theologians of the 20th century. He was made a cardinal by Pope John-Paul II but died two days before getting the red hat. In Mysterium Paschale he discusses what is meant by Jesus' "descent into hell" between his death and resurrection. A good summary can be found here in an article by John Webster of St John's College, Durham.

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The fundamental category in von Balthasar's conception of the atonement is that of solidarity. In this he moves significantly beyond some of the more familiar classical models--Anselm's "satisfaction" theory, the "penal substitution" of the later Calvinist divines--although the roots of his thinking are arguably deep in the patristic writings. For him, the mystery of redemption is the demonstration in the death of Christ of God's solidarity with the sinner who seeks to estrange himself from God.

To expand this theme, von Balthasar focuses not only on the events of Good Friday and Easter Day, but also on Christ's descent into hell on Holy Saturday. One of the strangest impulses to develop along this direction came from his close collaboration with Adrienne von Speyr, a doctor who was converted under him and who was the subject of mystical experiences of participation in the paschal sufferings of Christ. Von Balthasar later wrote of her that she "possessed in a special way a charism of theological insight. To the central insights bestowed on her belong the mysteries of Holy Saturday and hence of hell and universal redemption as well"...From von Speyr's experiences and writings, von Balthasar has taken the motif of the descent into hell as expressing God's refusal to abandon those who abandon him. Because he shares hell with the sinner, the sinner's willful attempt to live and die without God is forestalled. Even in hell, God himself is present in the Son. "On Holy Saturday there is the descent of the dead Jesus to hell, that is...his solidarity...with those who have lost their way from God...In this finality (of death) the dead Son descends...He is...dead together with them. And exactly in that way he disturbs the absolute loneliness striven for by the sinner: the sinner who wants to be 'damned" apart from God, finds God again in his loneliness, but God in the absolute weakness of love who...enters into solidarity with those damning themselves". However much the sinner may seek to put himself beyond God in "the complete loneliness of being-only-for-oneself, God himself enters into this very loneliness as someone who is ever more lonely...even what we call 'hell is, although it is the place of desolation, always still a christological place".