Nick of Time book by Ted Bell

This adventure is the story Nick McIver, a lad who sets out to become 'the hero of his own life'.

The setting is England, 1939, on the eve of war.

Nick and his sister Kate live in a lighthouse on the smallest of the Channel Islands. Nick, Kate and their father are engaged in a desperate war of espionage with the German U-boat fleets that are circling the islands prior to invasion. The information they provide daily to Winston Churchill is vital as he tries to warn England of the imminent Nazi invasion.

In a surprising twist, Nick discovers an old seachest sent to him by his ancestor, Captain Nicholas McIver of the Royal Navy. Nick returns to the year 1805 via a time machine and help save Captain McIver and, indeed, Admiral Nelson's entire fleet from the treachery of the French and the mutinous Captain Billy Blood.

In the climactic sea battle with Captain Blood, Nick's love of the sea, and his feats of derring-do, indisputably prove his courage and heroism.

His sister Kate, meanwhile, has enlisted the aid of two of England's most brilliant detectives, Lord Hawke, and Commander Hobbes, to thwart the Nazis. They prove themselves more than a match for England's underwater enemies, when they discover the existence of Germany's super-secret experimental submarine. In the end, Nick and Kate prove themselves heroes in the eyes of two of England's greatest Admiral Nelson and Winston Churchill.