The Dream Travellers — Sherry Ashworth

When a mysterious lodger called Dolf Hunter comes to live with 12-year-old Sam Kenyon and his family, it's the beginning of a seriously spooky adventure. For Sam has seen the man before -- in a nightmare. His friends decide to trail him and learn that Dolf makes straw-dolls that will allow them to visit each other's dreams. Each child has a separate dream kingdom; Sam's is a forest, Amy's a moonscape, while Dean's is in the mountains and Hannah's is centered on a most unusual city. At first, the children have fun visiting each other at night in their imaginary kingdoms, but soon they become increasingly aware that someone -- or something -- is stalking them in their dreams.