Normally a bad drama has a plot with holes in it. Spanish psychological thriller Muted is more like a black hole sucking in the occasional drifting nugget of narrative, destroying each one without trace. Rarely has such a serious-minded miniseries made so little sense.

We open with two people: a woman, followed seconds later by a man, plummeting to messy deaths from the top floor of a city apartment block. Six years later, Sergio (Arón Piper) is given early release from his juvenile detention centre: efforts to ascertain why he hurled his parents off their balcony when he was a teenager have failed, so a strange experiment is conceived. Sergio is allowed to return to the murder flat, but every room has been rigged with microphones and hidden cameras. As well as wearing an electronic tag, he is also being surveilled round the clock by a psychiatrist named Ana (Almudena Amor) and her team of investigators, who wish to study whether he is a danger to society. Why this ridiculously elaborate and risky scheme has been sanctioned is the first of many questions to which a satisfactory answer will not arrive.