The Monitor (2011) on Netflix

Plot summary

Anna and her son Anders take a large flat outside Oslo, relocated for safety because she fears her violent ex-husband may find them. Grete and Ole, the child care workers who visit, warn her that the boy's father could try to reopen a custody case. Anna at first makes Anders sleep in her room; when the two discourage that, she buys a baby monitor to keep watch on him. At the electronics store she meets Helge, a shy man whose terminally ill mother is in the hospital, and the two share their difficulties. One night she hears noises through the monitor, including screaming, and finds Anders asleep when she goes to him. Helge explains that the monitor can catch other frequencies nearby, and they try to trace the sound with a map that Anders has drawn.