'A complete triumph of imagination . . . readers are going to fall in love with this brilliant series.' – A.F. Steadman, bestselling author of SkandarAction adventure meets the time travel of Doctor Who in the second title of this epic series by bestselling award-winner M.G. Leonard. Perfect for fans of Adventures on Trains. Supports the key stage 2 curriculum. Illustrated throughout in black and white by Manuel Šumberac. Sim's Uncle Emmett is missing and on the run from the ruthless Council of Keys.Sim and his cousin Jeopardy are determined to find him.Their search takes them through a hidden door in time to Viking Norway and a desperate mission across land and sea to stop the legendary Gjallarhorn – said to herald Ragnarök, the end of the world – from falling into the wrong hands. The Legend of Viking Thunder can be read as a stand-alone novel, or enjoyed as part of the thrilling Time Keys series written by M.G. Leonard. Follow Sim and Jeopardy's adventures in the series in Hunt for the Golden Scarab and The Impossible Gladiator (coming in February 2026). Praise for the series:'Classic and fresh – a breathtaking adventure.' – Eoin Colfer, bestselling author of Artemis Fowl'A spellbinding, seat-of-the-pants adventure . . . fabulous, fast-paced and thrilling.' – Jonathan Stroud'A note-perfect, time-travelling blockbuster.' – Jack Meggitt-Phillips, bestselling author of The Beast and the Bethany