Linda Henry's character heads back to Walford in early December just as things are looking up for her ex-partner Phil, who appears to reach a positive turning point after his killer son Ben is sentenced.
Viewers will see Phil (Steve McFadden) resolve to concentrate on the Lexi case after Ben is handed a four-year prison term for the manslaughter of Heather Trott. Phil also finally makes his peace with Jay, who has been instructed to carry out community service for covering up the grisly crime.
Although Phil hopes to now move on from the tragedy of Heather's death, this may not be possible when a vengeful Shirley arrives back on Albert Square unexpectedly and declares that Ben's sentence was far too lenient.
Shirley soon has even more to complain about when she learns of Phil and Sharon's fake engagement scheme to bring Lola's daughter back home.
Suspicious over Phil's motives, Shirley lets Sharon (Letitia Dean) know about the hardman's issues with crack cocaine, casting doubt on his suitability as a guardian.
Phil later tries to reason with Shirley by insisting that he's just trying to do the right thing, but just as Shirley accepts this and is ready to leave the Square again, she is shocked to hear from Denise that Lexi is Ben's daughter.
Now convinced that Phil is just trying to control the situation for his own purposes, Shirley vows to stick around in Walford to scupper his plans - which begins when she tells Lola (Danielle Harold) that she's a fool to trust Phil. Will Shirley manage to throw a spanner in the works?
EastEnders airs Shirley's return on Monday, December 3 at 8pm on BBC One.