Watch Euthanizer for Free: How to Stream the Movie Online at 123Movies. . Euthanizer tells the story of a mechanic who euthanises sick and old pets as a side job. Despite the grim work, he has a soft spot for the animals. Trouble stirs when the owner of a dog he was supposed to end realises that the canine is still alive. The only innocent party in the drama that ensues is the dog itself.