Christian time travel

In a response to reading L'Engel's "An Acceptable Time," Pentimiento
asks:

"Is Christian time travel possible?"

....Polly and Bishop Colubra find themselves in extreme danger three thousand years ago, and are unable to transfer themselves back to the present. While Polly has more faith in science than in God, the Bishop invokes the mercy of Christ in ways both subtle and obvious -- intoning the Kyrie when he's been captured, for instance, and assuring Polly that Christ existed even a thousand years before His birth. However, he also believes that the ancient druids possessed knowledge that has now been lost -- knowledge, for instance, of the techniques of time travel -- and I suppose that it is these statements that a critic like O'Brien would call heretical.

Now, I don't want to set up a straw man, because I haven't read O'Brien's polemic (though I do have it on order through interlibrary loan). If anyone has read the book and can set me straight, please do so in the combox. But it seems to me that, if you believe that we exist in both time and in eternity (which is what we believe, isn't it?), it is not heretical to believe in the possibility of time travel. We already know that it is good and meet to pray for the dead as if they were still alive. Nor is it heretical, is it, to suggest that ancient peoples and pre-Christian cultures possessed knowledge that has been lost to us? Can't one believe in Jesus Christ as the Lord of and the fulfillment of human history and, at the same time, acknowledge that non-Christian lands and people had a great deal to offer?

I suppose the problem comes when we try to resurrect lost knowledge in its original context, rather than baptizing it in the light of the salvific proclamation. Of course, we should not try to use any power to circumvent or second-guess the will of God, and part of the discipline of Christianity for some who have the special gifts of which Saint Paul speaks is the laying aside of those abilities in favor of accepting smallness, weakness, and utter dependence on God. But, contra O'Brien, I don't believe we should be afraid to read any literary suggestions of special gifts existing in a non-Christian context, or about time travel, or about snakes or dragons who are good rather than evil.
-Pentimiento, link