Harriet, Jake and Mathew are enjoying a holiday fishing trip when suddenly a strange mist descends and surrounds their boat. As it clears, the three children find themselves mysteriously transported back to the year 1808. Anchored majestically ahead of them is the mighty sailing ship, The Intrepid, a great man o' war. Sea shanties echo across the waves as eleven year old Jake is brutally captured and taken to serve in the Napoleonic Wars. Will Harriet and Mathew be able to rescue Jake and bring him safely back to England? Will they be able to assist the desperately wounded soldiers from the carnage of the battlefield? Will they survive the grim battles and storms at sea before they are once more returned to twenty first century Britain?