While half the team are off tracking down escapee Ward, Skye and Coulson continue their investigations into the mysterious writing that Phil is compelled to carve into the wall. Skye instinctively knows it's a map... but to, or of, what?
A brutal murder where the victim has had the symbols cut into her body sparks memories in Coulson that the woman is actually a S.H.I.E.L.D. agent - and her paintings of the symbols suggest she has some connection to their quest.
Phil decides to go back into the "memory machine" and discovers that the murder victim along with five other agents of S.H.I.E.L.D. were treated, like Phil, with the GH325 drug in life-saving/restoring operations (obtained from the blood of the dead blue alien; we can call him a Kree now, right? That particularly secret is well and truly out unfortunately). All were overwhelmed by the memories carried in the blood and the only way for S.H.I.E.L.D. to treat them further was erase their memories and implant new ones... as happened with Coulson.
Coulson and his team quickly deduce that the killer is one of these patients and as only two are still alive they head to the home of the nearest.
However, it turns out they weren't the only people heading there.
Meanwhile Ward and Agent May's team are playing cat-and-mouse across the country, with Ward seemingly always one step ahead.
I'm just hoping Ward gets the reward he justly deserves, preferably at the hands of Skye, Coulson or May. He's not a nice man and Brett Dalton is clearly reveling in the role, now he's been let off the leash and doesn't have play Ward as a plank of wood.
The Writing on the Wall was a clever blend of pure spy-vs-spy action, in the Ward plot thread, and freaky, sci-fi worldbuilding in the main thread that led to the final revelation of what the carvings actually showed (is it too early to say Attilan? Although I am wary that this might just be wishful thinking from fans as the Inhumans movie isn't hitting until November 2018!)
Now that the 'code' of the mysterious (Kree?) writing has been cracked, to a certain degree, the plotlines of Agents Of S.H.I.E.L.D. can now move forward towards the 'lost city' and Coulson's race to find it before Hydra does.