The BBC Press release says
St Timothy's is one of the UK's top teaching hospitals, home to some of the country's most promising trainee doctors. But beneath its veneer of medical normality lies a secret network of dangerous experiments pushing back the boundaries of science with potentially horrifying consequences in this one-off 60-minute medical horror drama written by Paul Cornell.
Hannah Carter's mother was a consultant at the hospital, but died suddenly a year ago. Grief left Hannah (Claire Foy) teetering on the edge, but following a year off, she's back to resume her training. But Hannah remains fragile, so when she starts glimpsing peculiar events in the hospital and unsettling behaviour from her ex-boyfriend and star surgeon Nick (Stephen Campbell Moore), she's unsure what to believe.
Ignoring the pleas of those around her, Hannah puts her sanity on the line to uncover the truth about the hospital"
It's good. Bloody good.
The opening scene, (which I hope I can forget if I ever need to go into hospital for an operation) gives viewers a glimpse of what is happening (although not how or why) - letting us know more than Hannah does: enough to make us fear for Hannah's safety as she begins to look into the anomalies she witnesses, and to realise what is happening.
Hannah and the other characters are believable, and even in the confines of a single episode we see them start to develop in a realistic and believable way, and learn more about Hannah's past, without heavy-handed flashbacks or exposition.
There are some bloody moments, but this doesn't rely on blood for its horror.
In short: Pulse is very well written, tightly plotted, and left me at the end, staring at the screen and saying "but I want to know what happens next.."
I really hope the BBC commission a full series so I can find out. And you should definitely watch this whenit airs.
You might not want to watch just before going into hospital, though.