A Space Agency detects a signal from outer space. Unlike most shows, this is not NASA - it is the French Space Agency! This show is obviously an Anglo-French production, despite being distributed by a US TV network.
To add a bit of excitement, it turns out that someone or something is going to use an EMP attack that will kill any humans who are not in a shielded location. Most of the main characters rush to get underground.
The EMP has killed everyone who was not underground. Somehow an elevator can shield people, but not a car. Also, somehow dogs (and presumably other animals) are immune. The bit about the dog is not a clumsy goof but an intentional part of the plot. Bill Ward (Gabriel Byrne Excalibur (1981) ) actually points it out.
The French soldiers go out to find survivors. Typically of soldiers in movie and TV shows, they do not have helmets or infrared goggles. Well, they have to look telegenic. There are a few looters who take all the food and water. Also, something is collecting all the dead bodies.
The British Army sends out a patrol, and they have the same problem that the French did. In fact, this is worse because they have no recognition signal at their base. Yes, the man opening the front door has no way to verify if the person on the other side is friend or foe.
Bill Ward (Gabriel Byrne Excalibur (1981) ) discovers a few secrets of the alien invaders. They look like robotic dogs, with pneumatic bolt-guns for heads. Inside is a cerebral cortex, so they are at least partly organic. Since the aliens used an EMP that specifically spared dogs it is possible that the brains are actually cloned dog tissue. The alternative is that the aliens are dogs, and their genocidal war to exterminate all humans is their attempt to liberate the dogs that mankind has enslaved. This is no stranger than the storyline of Westworld (2016) , which is basically the story of Terminator (1984) as told from the perspective of Skynet.
Elsewhere, the woman and her tweenage kids continue their selfish journey to whatever remains of what used to be their home. They get sidetracked to help other survivors in a hospital. Somehow, the man that they left for dead has gotten there before him.
The hospital gets attacked by the robot dogs. Rather than stay and fight, the humans plan to run. But what about the babies in the maternity ward?
The French army sends out a patrol to locate the source of the alien signal. As always, they have kevlar vests ... but no helmets!
The French civilians meet up with a French police unit. This allows a bit of domestic drama, something that would be better suited to a cheesy soap opera.
The French police unit finally realise it is time to move on. They get chased by the robot dogs, and nobody acts like a sensible person. One forgets they have an automatic weapon, while another does not bother to shoot an easy target. The third idiot can be ignored, since his motivation is revenge and his deliberate action actually makes sense.
The French Army locate a crashed alien spaceship, and try to find the component that is transmitting the signal.