I actually don't have a problem with that. Sadly there are plenty of cases of people who killed because they thought it was fun.

OK. If we break this down...
Rick - Motive = Celine (her comment re dads and daddy issues), Lindsey (to protect Robbie and Jason), Tegan (??), Dr Savage (??), Kim
Diane - attempt - Celine (her sister had issues with Diane, mummy/cheating issues, helping Tegan), Tegan (baby swap), Lindsey (??), Dr Savage (cheating issues/ covering up Marians mistake), Kim (if she isn't really Kim and Kath, could be re swap)
Marian - Celine (helping Tegan), Tegan (baby swap), Lindsey (due to her screw up), Dr Savage (wanted rid as ex wife), Kim (??)
Phoebe - Celine (some weird jealousy at her getting real attention as she "wasn't real family"), Tegan (?), Lindsey (to protect Joe), Dr Savage (?), Kim (??)
Esther attempt - Celine (?/ unless she resents Esther from taking a babe from its mum as she has mummy issues), Tegan (same reason - keeping baby from mum), Lindsey (some weird way of keeping grace onside and protecting Freddie), Dr Savage (??), Kim (takes guilt out of the equation and the problem away)
Celine and Tegan look most obvious!

In the Mariam case, Celine let Mariam into S'Avage's office (although she was tricked into it.) Had Mariam reported her, Celine would probably have lost her job. That could be a motive for murder.

It's also common knowledge that Diane lied to the police to protect Finn, which could be a reason to go for her ...

I'd like it to be Celine.

You're probably right there, I won't hold my breath for a decent explanation. I'd love for Oaks to surprise us all and somehow come out with a well crafted story where things join up and make sense, but it'd be silly to believe it'll happen.

Wasn't Dodger being Nico's dad a well-crafted and completely plausible storyline?

She is the one who makes most sense as to killing for the greater good (with Dr Savage close behind). Tegan - they could use the cancer as to why she'd do that, but Lindsey does not seem to fit the bill. And Kim - I don't know. She has done enough bad that I can't see crazy Kim's mind killing for the greater good. As crazy as she is, she just doesn't fit the profile of the murderer for me. I still say Dr Savage or Celine.

Lol, not quite what I meant but there is that. Ah accidental twincest, such a gritty, realistic and entirely relatable story.

All the suspects seem to obvious! They've all been hinted at apart from Lindsey and Celine...

I think it'll be someone from the outside.

Celine's been made to look suspicious several times (in Rick, Diane, and Mariam's cases.) Lindsey was the one in the spotlight over Phoebe's murder: she wanted to keep the details of the shooting quiet, she tried to convince the McQueens not to consent to Phoebe's surgery, and she admitted she had strong personal feelings over Phoebe because of Kath.

Which doesn't quite fit the bill for killing for fun though does it?

Kim is the obvious choice so I don't think it's her.

Possibly Lindsay.

No, that's true ... on one hand the show was clearly trying to put the heat on Lindsey there, on the other they were saying that the killer just did this for laughs? The only ones without a personal "stake" in Phoebe were Tegan and S'Avage ...

the last couple of episodes seem to be trying to make us think its Kim

In, fact, they are making it too obvious for it to be Kim

I would go with Lindsey at this stage - no idea why tho

Please let it be Tom or his grandmother or even Peri
Makes as much sense as some storylines

For no real reason (as i said earlier, i doubt the writers have decided who it is yet) I think it will be Tegan. Or Rose West has escaped from jail and is having her wrath.

IAreSam said there is one writer who is the brain behind the GHK story and knows who it is. That said though it wouldn't surprise me if Birkwood changed it at a moment's notice to suit whatever he wants.

They're supposed to be ruling out one suspect this summer, I wouldn't be surprised if it's Kim

are they? my guess would be Kim as well then

Yep. I'm guessing they make it look Esther will die and then they'll pull a fast one on us. Or they'll kill em both off, who knows these days?

Way too obvious now to be kim. Im assuming kim injected something into Esther's drip to kill her then the real GHK was trying to do the same thing but she flatlined before they could.

Lindsay, but I'm not sure.

Kim is too obvious.

Myra Pocahauntus

At the very beginning I thought it was Celine. She hasn't done much since arriving - maybe she is the killer and we're supposed to forget about her?

I still think Lindsay doesn't fit the "profile". Nothing about her character screams acts for "the greater good". She seems pretty aware of right and wrong even if she makes the wrong decisions. Kim too...she is far too busy obsessing over grace for this. And it is now imo too obvious for it to be her unless the twin is not a vegetable and been posing as Kim at some stage! Celine and Dr Savage totally fit the profile, although I'd question, with feline's insecurities that she is really capable of believing she is doing the act of "greater good" now. Tegan - it would have to be linked to the cancer, but for her to try and kill Esther would really suggest she has lost the plot and doesn't she have enough going on. Celine would be the biggest shock as she is the only one out of everyone who really hasn't shown a dark side and I think it could tie in nicely with her abused as a child, then "sacrificed for Cleo" as she got too old. I still find it odd why she is so bothered about Pete's opinion on what she wears etc...