Thyme Running Out (The Tartan of Thyme #2) by Panama Oxridge

Justin Thyme is a self-made billionaire living in a castle overlooking Loch Ness. The day he turns thirteen, he receives an anonymous gift: a fabulous watch with a puzzling message hidden on it. When he tells his father of his plans to build a time machine, the Laird of Thyme reveals tantalising fragments of past espionage and warns his son of a ruthless enemy keeping him under constant surveillance.
Suddenly, the race against time is on. Can Justin convert his vintage motorbike into a time machine, rescue his mum and discover the identity of their resident spy in less than a week … or will the dreaded Thyme Curse claim another life?