Timothy Fitzwillian comes into David's ken one day while David is in the abandoned gardener's cottage at Grayson Hall, before it was renovated to become The Violet Garden. In the bedroom he discovers an old volume, "A Pilgrim's Progress" with "This book is the property of Timothy Fitzwilliam" on the inside cover. Feeling a strong connection to the boy, David takes the book and a little tin fire truck with him, but he temporarily forgets about them with the subsequent whirlwind of activity.
When Lia arrives at Beak's End, David shows her the book and fire truck. Inspired, they do some internet sleuthing and track down Timothy. A special friendship is born.