Timesnatch by Robert Swindells
Once a creature is extinct, it's gone for ever, isn't it?
Not any more - as a butterfly from the past proves. The physicist mother of Kizzy Rye and Fraser Rye has invented an amazing time machine that can travel back into the past, snatch a plant or animal now extinct and bring it back into the present.
It's a wonderful achievement, a real scientific breakthrough. But the machine - 'Rye's Apparatus' - has a horrifying potential. Suddenly Kizzy and Fraser find themselves caught up in a terrifying spiral of events - events that lead finally to a monstrous demand from a sinister and violent organization...
WINNER OF THE 1995 EARTHWORM AWARD, 7-11 YEAR-OLD CATEGORY