Don't let the cutely-designed cartoon robin and owl (the latter voiced by Brian Wilde!) fool you. There are a lot of moments in this film that are quite grim, upsetting or nightmarish. The 70s synthesized music can get rather ominous at times. And there are some (pardon the pun) SHOCKING moments here. There's a teenage boy who is helping roll a boat with a long metal mast on land, and the mast touches a power line and knocks the boy unconscious with an electrical shock as the girl with him screams. According to the owl, the boy was OK after a few days, to the relief of his robin friend.
Then we have a boy fly his kite right into a high-voltage power line carried by electrical towers (or "pylons" as they're called in the UK), and he is also zapped, and was burned in the process, but thankfully not fatally. We get the message that if your kite or model airplane is heading right towards power lines, let go right away before they touch, and if you need to get them back, let the police or the electric company handle it.
Then this leads to the most famous part of the film, about substations (which is what they call transformer power stations in the UK). Two kids, a boy named Jimmy and his female friend, accidentally toss a Frisbee into a substation, and the girl orders Jimmy to go break into the substation and retrieve it ("There's a gap down there! A gang of kids broke in yesterday. I saw them!" the girl says.) The music gets spookier, as the boy runs around the intimidating electrical equipment, ignoring the "DANGER" sign, but right as he attempts to retrieve the Frisbee, he is graphically and fatally shocked (we see his pants catch fire, too!) as his friend yells "JIMMYYYYYYY!" This upsets the robin as well, and vows to play safe.
And then there's a bit where it's not always the stupid people fooling around with electricity that are victims, and we see a group of rowdy teenagers toss a chain at an electrical tower, causing a nasty mini-explosion and short circuit that causes a power failure in the area, and with the streetlights and traffic lights out, the lead teenage boy's younger sister is hit and killed by a car while riding her bicycle in the darkness. This angers the robin, saying he'd like to get his claws on the rebellious teenage boy that did it.
The main message the film conveys is to play safe, i.e. stay away from power lines and substations; don't fish or boat in water near them, and don't fly kites or model aircraft near them, and don't play in or near substations.
60-second excerpts from this film (starting at the 2:35, 4:00 and of course 6:30) were also televised in the UK as individual public information films, well into the 1980s. The latter "JIMMYYYYYYY!" one was deemed as the most shocking (no pun intended this time) and unnerving...
Of course, we had a few different electrical safety films and presentations when I was in school, and I learned "DANGER" at an early age thanks to this Sesame Street music video that screams 80s!
I apologize for any nightmares I cause with that public information film!