A lot has happened since Tim experienced the adventure of his life at Loch Ness in Scotland, when he found his father and reunited his family.
It is the last day before the summer break and he and his father Eric are looking forward to their vacation in Borneo, one and a half years after Tim’s mother Anna was killed in a tragic car accident.
Eric is completely unaware that Tim has no intention of travelling to Borneo – he has secretly rebooked the airline tickets to Scotland. Tim yearns to again return, together with his dad, to the one place where his family was happy together. It is also the only possibility Tim sees to nudge his father out of the reclusive life he has been leading for the last several months.
But the opposite proves to be the case: as soon as father and son arrive at the idyllic castle Heartspring at Loch Ness, Eric immediately wants to go home. He is overwhelmed by the memories of his deceased wife Anna.
Tim, though, is ecstatic at being back at his beloved Loch Ness. Rummaging through the old castle he finds a mysterious map covered with cryptic Celtic characters. Could this map possibly contain any clues regarding the existence of the legendary monster of Loch Ness? Could it even reveal Nessie’s whereabouts?
Eric is extremely skeptical: as an oceanographer he has dedicated ten years of his life to the unsuccessful search and is familiar with every existing map and every known clue to the elusive creature. He therefore assumes that this map is yet another forgery meant to put them on the wrong track. Tim believes otherwise, so the little adventurer secretly sets off on his own quest.
Taking a boat, he crosses to the distant shore of the huge lake to explore the mysterious woods of the Scottish highlands.
What Tim does not suspect is that an old adversary has already gotten wind of the map’s existence – but more importantly – that the map is authentic!
Paul, a former colleague of Eric’s, is hot on Tim’s trail, accompanied by a group of big game hunters under the command of the wild Sheila. Meanwhile, Eric has discovered Tim’s plans and together with the beautiful Emma, sets off on a desperate search for his son.
But Paul and his hunters have already captured Tim. Unable to escape and continue his search for Nessie, only the sudden appearance of an old friend saves Tim from Paul’s clutches: Oki, the 605-year-old druid. He has his own motives for finding the legendary monster, which turn out to be way beyond Tim’s wildest imagination…