The elevator pitch: 

what if Waco happened in posh Chelsea?

read/skip:

READ
Lisa Jewell builds wholly believable universes and delves into their complex life stories of ordinary people like not many can in the thriller genre. When I lived in London, my favorite thing to do was bike along the Thames until I arrived in Chelsea. The houses at the river are the kind that made you wonder; what kind of people own these, how rich are they, what do they do, day-to-day? Lisa Jewell looked at one of those houses and imagined a twisty take of deception, lost souls, abuse, love, desire, and hope.
In a character-driven mystery, you need novelty, and sympathetic characters are required to give the story the same propulsion as an action or murder-packed thriller. She nails it. Again.
Jewel often uses a multiple POV; it’s not my favorite storytelling device. There is always one character that falls short. The one that makes you speed and skip through chapters. Not so much in The family upstairs, but I liked the two female characters the most.
Libby works at a kitchen design store; she is our In into the story, it is easy to empathize with such a levelheaded and sympathetic girl. The second one is Lucy, a 39 woman, living a rough life on the streets of France with her two small kids. It isn’t immediately clear what her relation to the story is, but her story is engaging, and you root for her.
The one I didn’t enjoy reading as much about is Henry. Henry is the one that tells the main story. Henry
is also the one that messes up the story. Henry is one hell of a shifty character. Is he a victim, a killer, a liar, or a savior?
 When Henry changes his story, it’s a bit clunky and doesn’t always provide the big twist it intends to. And Henry is off-putting from the start ( and seeing that he is the gay character a bit problematic). But I am nitpicking here; it is just that the other parts are engaging, you want every aspect to be at that level.
This is a tragic tale about a cult leader ruining lives and could be overdone but is told in an original, well-constructed way and satisfying way. It is richly imagined, the kind of story you wholly buy. I always assumed happy lives in those houses, but now I will never look at one of them the same.

The gist: 

on her 25th birthday, Libby learns that her birth parents left her a mansion in Chelsea. The same mansion where they were found dead, together with an unknown man, in what was ruled a suicide pact. Libby herself was found in that house as a baby and saved, but the other four children who lived there, all teenagers at that time, all disappeared into thin air. Libby has to decide what she will do with the million-dollar property, but first, with the help of a handsome journalist, she wants to uncover the truth.