The first book starts off with a talking four legged animal walking down the street and then tells of how 4 siblings, 3 girls one boy (one girl many have been named jane and skipped a grade) (one girl was a lot younger than the rest and could like talk to animals or something) go to a magical world where morgana Le Fay was. The seco6book they think something is wrong with the magical world, earthquakes happening, they call the cops because the old lady(morgana Le Fay?) Was missing and go to the magical world. I don't remember if there were more than two books
Four children set out to rescue a sorceress held captive in a parallel world.