A message through time

When 11-year-old Felix finds a message in a bottle during a trip to France, he is in for the surprise of a lifetime. Suddenly he is flung back 1700 years to Ancient Roman times, dragging his very unwilling 15-year-old stepsister, Zoe, with him. They are offered sparrows for lunch and horse-spit as medicine, but that is only the beginning! When they ricochet forward to their own time again, Felix and Zoe discover they have accidentally brought a high-class Roman girl with them. Can they navigate the strange Roman world -- from opulent city to distant sacred spring -- and return the 12-year-old girl to her family before time runs out?