This book is about two siblings, a white boy and girl. They live in Newfoundland. They find in their house, somehow, a strange box with knobs and a strange purplish light coming out from the bottom. They take it outside one night and start fiddling with it. One knob makes time go backwards (like in The Time Machine). When they stop it, they find themselves several hundred years in the past, in the time of the Beothuks. They are captured by a tribe and lose the box. They are almost roasted while tied to a pole, before they escape and recover the box. They are successful in returning to the time they left, but a little later. Later when their father is digging in the garden, he digs up the tool they used to escape from the pole.
They later learn that their (parents? grandparents?) know full well what the box is for and give them the instruction manual for it, which implies a sequel.
The cover shows them kneeling outside, among the pines, with the box in front of them, emitting the purple light, which outlines them. The cover is otherwise black. Title and author at the top of the cover, in blue.
The book was probably printed in the early 1990s. I read it at my school and also saw a copy in a local bookstore. It may have been printed in Canada or Newfoundland. The title was short, no more than two or three words. The authors name was two words.
It was at least an inch thick, no more than a hundred pages, softcover. There was a map showing where they lived (I think) It is not Blood Red Ochre.