Webster's Leap, by Eileen Dunlop (Holiday House, 1995, middle grade, 168 pages, published in 1995 in the UK as Castle Gryffe)
When Jill's parents divorced, she stayed in London with her mother, and her much loved older brother, Tad, went to live with their father. At first Tad and Jill were able to stay close, but when her father took Tad to live in Scotland, he seemed not at all sorry to go. Jill took it personally, and her fondness for her brother turned cold. And so in the summers Jill and Tad swap places, and have nothing to do with each other. This particular summer, Jill finds herself in the wilds of Scotland, at Castle Gryffe, where her father is the caretaker.
Bored and resentful, Jill wanders the empty rooms of the castle, where there is little that interests her. But all that changes when she starts up Tad's computer, and clicks on one of his files about the castle--and finds herself back in the 16th century, when Mary was still Queen of Scots, and the castle was bustling with activity.
She has a place in the past, into which she slips seamlessly--she is the young protegee of the castle's lady, who is lovely, save for a birth defect that mars her face. And Tad is there too, serving the lord. There in the cold winter of Castle Gryffe the chill between brother and sister vanishes when they are confronted with a horrible plot to accuse the lady of the keep of witchcraft. Unravelling the plot will take courage and determination...and working as a team.
This is the sort of book that will delight and enthrall the 10 or 11 year-old girl who daydreams about the past, the sort who imagines slipping back into the past whenever they visit an old castle, but Dunlop manages to keep her Scotland nicely unromanticized. I felt she did an excellent job capturing what life might well have been like in a cold and not particularly wealthy castle back in the 1500s! And although the first third of the book might seem slow--it is primarily concerned with Jill sulking around in the present--once the time travel gets going, there is plenty of mystery and intrigue for those who like things to Happen, and the tension builds most satisfactorily to an exciting climax.
So although I'm not going to say that you Must go find this book at once, if it should still happen to be in your library system, and you like a nice time travel, go for it! Dunlop is an excellent writer (in fact, she wrote one of my Favorite Books Ever, A Flute on Mayferry Street (aka The House on Mayferry Street in the US, my review), and although this book isn't nearly as magical, I enjoyed reading it. I probably would have LOVED it back in the day....when I still had my collection of unicorn stickers.
(one thing that made me chuckle was how dated Tad's computer is--Jill has to insert a floppy disk).