Children of the Dog Star (1984)

12 year old Gretchen comes to stay on her uncle's farm for the holidays, but shortly after her arrival strange things start to happen. Gretchen has a passion for science and a talent for all things mechanical, which is why the old brass weathervane fascinates her. But the brass daisy rod has a complex and terrifying significance, and Gretchen and her new friend Ronny discover its links with the far distant Sirius, the Dog Star.