Sarah cheated on Adam with dodgy Damon (Griffiths), who was then driven out of town by a vengeful Adam, forcing him to abandon his business interest in the Bistro.
Meanwhile, Damon's half-brother Harvey (Mellor) is currently behind bars for the murder of Natasha Blakeman (Rachel Leskovac) - mother of Sarah's nephew Sam (Jude Riordan) - and is not best pleased with Damon either.
"It kicks off almost in the first moment of the new year. [We're] revisiting the unfinished business between Adam, Sarah and Damon," exec producer Iain MacLeod told press recently, in quotes reported by the Radio Times.
"So, we arrive in the new year, Adam and Sarah are rubbing along okay. They're trying to amicably co-parent Harry as per their agreement when they split up, and it's going alright, and then suddenly, wallop, Adam finds himself in this nightmare situation, all at the hands of Damon - who's unexpectedly come back.
"He was obviously, as you may remember, run out of town by Adam, and in our minds has been somewhere away from Coronation Street plotting his revenge, and it arrives as a fairly blunt force on the first episode of the new year.
"The story then becomes a kind of a triangle, where we also imagine Damon has been spending his intervening months pining for Sarah. I felt there [were] really intense feelings between those two and really natural chemistry and connection, and he comes back with a kind of two-pronged plan.
"The first of them is that he wants to get revenge on Adam, and the second is that he wants Sarah back, because he feels like she's the one - and he will essentially have to contend with the fact that these two plans might not be compatible. Like, can he have his revenge and also have Sarah? The answer might well be no, so which one is he going to choose?"
Explaining Harvey's involvement in the story, he continued: "[Adam] decides in his mind that to protect Sarah he might want rid of Damon, so as Damon's calming down, Adam's going in the other direction, and his plans to rid himself of Damon will see him pay a little visit to Damon's half-brother Harvey, because he's no fan of Damon's either - and they might form this unholy alliance.
"They have a shared problem in the form of Damon, and think they can help each other in that regard. It's got fantastic actors in it, as all our stories do; the storyline is packed full of twists and turns and excitement.
"Dare I say it in this day and age, but it's quite sexy, as well. I think that it's got lots of intensity and passion and a whirlwind romance for Damon and Sarah."
The returns of Damon and Harvey come amid a flurry of arrivals and returns over the festive period, with Tommy Orpington (Matt Milburn) and Bethany Platt (Lucy Fallon) coming back to the cobbles alongside the introduction of Carla's nephew Bobby (Jack Carroll).
Coronation Street continues Mondays, Wednesdays and Fridays at 8pm on ITV1 and ITVX. body check tags ::