With the Home Timeline running out of resources to feed its people, the invention of cross time trafficking was a literal lifeline. Need a new oil field, just find a history where there was no human life. The same for iron, gold, silver...

Want strange new foodstuffs? Or the same old ones, but without the hassle of having to grow them yourself? Find a Reality that the space to spare, or a population capable of growing them. But with people there's danger. Danger of Crosstime Inc's secrets being uncovered, danger of disease, and danger to Crosstime's agents in that reality...