Episode three of The Sister finally provided us answers about how and why Elise died following that fateful party - and whether or not her death was entirely accidental.
However, the explanation left viewers with yet more questions ahead of Thursday night's series finale, including just how far Nathan will be prepared to go to keep his wife Holly from discovering the truth.
The Sister cast includes Russell Tovey (Years and Years) as protagonist Nathan, while Doctor Foster's Bertie Carvel plays the sinister Bob, a "ghost whisperer" - whose intentions finally became clear in episode three.
*Warning: spoilers ahead for The Sister episode three*
Did Holly hear Elise's ghost in the house?
Near the beginning of the third episode (following the flashback to Nathan and Holly's wedding), Holly is left alone in the house at night.
Heading towards the computer, she's stopped in her tracks when she hears a creaking upstairs and the sound of footsteps - the same noises we heard at the end of The Sister episode one, when Nathan was also alone in the house and dared Elise's ghost to make herself known, which she appeared to do by turning the garden lights on.
For viewers wondering if The Sister is based on a true story, the four-part series is based on creator Neil Cross' book Burial, which in turn was inspired by a nightmare The Sister creator Cross had in 1985 about murdering a homeless man - in addition to a haunting Cross experienced.
Did Nathan sleep with Elise before she died?
In short, yes - which makes Nathan's betrayal to wife Holly even worse.
In a flashback to the fateful night, we see Elise catch up with Nathan on the walk home from the New Year's Eve party. They flirt, before Bob's car pulls up and he offers them a lift to a nearby wooded clearing, which is supposedly haunted by the ghost of a young woman.
Bob is downright creepy, handing Elise some cocaine before seeming to encourage the pair to have sex in the back of his car once he's gone for a walk - which the couple do, after Elise (and only Elise) takes the drugs.
How did Elise die?
Still in the back of Bob's car, Elise appears to have a fit or seizure apparently brought on by the drugs. She jolts from side to side, before smashing her head against the backseat window.
As Bob and a tearful, panicky Nathan examine her body, it's not clear whether it was the drugs or her head trauma that killed her, and Bob places the blame squarely on Nathan, repeatedly shouting: "What did you do?"
Where has Bob hidden Elise's body?
Earlier in episode three, Nathan and Bob (in the present day) head to the wood where they buried Elise's body almost a decade earlier. They then dig up and place her remain's in the boot of Bob's car, before arriving at his lockup, where Bob (who seems to have thought of everything...) already has a freezer ready.
However, when Nathan sneaks back to the lockup later in the episode, he finds that her remains have been moved - and after breaking into Bob's house, he seems convinced that there's something hidden in Bob's metal safe.
For details on the spooky wood scenes, have a read about the The Sister filming locations.
Did Bob kill Elise?
After spending years wrongly believing that he accidentally caused Elise's death, Nathan finally discovers the truth: Bob murdered Elise.
Bob reveals at the end of episode three that he had seen Elise as an "opportunity" to create a ghost - and "nudged" things along in order to have the perfect conditions for a haunting (including encouraging Nathan and Elise to have sex).
Of course, if the drugs Bob gave the couple were poisoned, doesn't that mean that Nathan was meant to die, too? And once Nathan realises this, will he seek revenge?
You can order Neil Cross’ Burial from Amazon. The Sister finishes on Thursday 29th October 2020, on ITV and ITV Hub at 9pm. Check out what else is on with our TV Guide, or take a look at our new TV shows 2020 page to find out what's airing this autumn and beyond.