Need the title of a french book? Please help.?

It starts in the present, where people are digging and they hit snow, they find 2 people in it. It takes place somewhere in canada. The people thaw and it turns out they are from the past and they claim how perfect the past was. The present day people spend a long time trying to figure out how to feed them. They don't eat food. They take pills to be nourished. There is love story between the female frozen person and the main guy who finds them. It ends by us finding out how they survived the apocalypse of the past time (possibly different universe????)