Hmm. I'm torn. One the one hand, I'm thrilled that Flack will finally get some development and that we're finally getting to see other members of Clan Flack. Flack fans have been clamoring for this for years, and with a spectacular actor like Eddie in the role, I've no doubt that he will turn in some stellar performances. I'm also pleased that the femme Flack won't be used as a mere spot of window dressing.
However...
This could be a disaster. The writers are fond of ratcheting up the drama to the point of uncomfortable melodrama at times and have a nasty habit of either dropping storylines(Louie) or ignoring the logical consequences of a given action when it doesn't suit their purposes(Stella initially covering up her possible exposure to HIV and the subsequent compromising of the crime scene by her riffling through the medicine cabinet, Lindsay refusing to pull her weight during her resurrection and ceaseless flogging of her Montana Drama Llama, Mac ignoring protocol in the Clay Dobson mess, Stella letting a confessed murderer escape because of their childhood ties). Anything that might result in unpleasant, real-life consequences for Our Intrepid Heroes gets swept under a large(and very filthy at this stage)rug.
So, let's say Samantha Flack is "trouble", a manipulative, conniving brat who uses her brother's innate sense of loyalty to her advantage. What does that mean? Is she going to ask him to cover up her involvement in a crime? If so, it would certainly create a nice parallel to Gavin Moran in S1's "The Fall", but it also creates a nasty bailiwick. If Flack chooses to compromise his integrity as a police officer and cover up evidence, then there can only be one logical outcome. He must be caught and arrested and booted from the force, and as a logical extension, from the show. Such a momentous action should have equally momentous consequences.
But I doubt the show wants to lose Mr. Snark, and so I doubt such consequences will ever be on view. Either no one will ever get wind of the cover-up, or the writers will contrive a lame and patently unbelievable cover-up that safeguards them from having to make a difficult decision. Either that, or good and honorable Flack will drag his friends into the conspiracy of silence and tarnish multiple careers instead of just his, hence the involvement of Adam and Stella. Whee hee. God, this sounds worse the more I type.
Granted, this is all rampant speculation, and it could turn out to be nothing so dire. Maybe Samantha Flack has a drinking or drug problem, which would explain his knowledge of the Withers Clinic in S2. Maybe he finds himself trying to protect her from bookies or dealers. The possibilities are myriad, and nothing is certain until the episodes air.
This could be fabulous, and I really want it to work for the sake of both the actor and the character, but with the writers' godawful track record of providing satisfying story arcs with logical resolutions and TPTB's reticence to take risks, I have serious, serious reservations about their sudden decision to expand a role that was originally intended as a bit part in one episode. It sounds too much like they've found a shiny, new toy and want to play with it, but have only vague ideas on how to use it.