Billionaire Solomon Daisy is obsessed with the skeleton of a blue-eyed girl from Roman London. He has managed to invent a time machine so that he can go and find her, but it's estimated that for each hour spent in the past, the time traveller's life will be shortened, so Solomon recruits a potential child time traveller: Alex Papas, a 12-year-old boy who knows a smattering of Greek and Latin. Alex's mission is to go back to Londinium through a portal in London's Mithraeum and find out all he can about the blue-eyed girl. But time travel is no picnic - and Roman London is far more dangerous than anyone could have known.
