Half a screen. My Sony TV is about 4 years old and while the sister-in-law- was watching a movie

Question

My Sony TV is about 4 years old and while the sister-in-law- was watching a movie the screen halved. The whole picture can be seen but only on the bottom half of the screen, the top half is just black. There isn't a vertical hold adjustment k**b that I can find so I need a bit of help here. Thanks.