You’re gone and I gotta stay
high all the time, to keep you off my mind.
Spend my days locked in a haze, trying to forget you babe
I fall back down, gotta stay high all my life,
to forget I’m missing you. Staying in my play pretend,
where the fun ain’t got no end.
Can’t go home alone again, need someone to numb the pain.

Unter Halluzination versteht man eine Wahrnehmung eines Sinnesgebietes, ohne dass eine nachweisbare Reizgrundlage vorliegt. Das bedeutet zum Beispiel, dass physikalisch nicht nachweisbare Objekte gesehen werden oder Stimmen gehört, ohne dass jemand spricht. Halluzinationen können alle Sinnesgebiete betreffen. Bei einer Illusion hingegen wird ein real vorhandener Sachverhalt verändert wahrgenommen: Ein tatsächlich vorhandener feststehender Gegenstand scheint sich zu bewegen oder in irregulären Mustern werden scheinbar Gesichter erkennbar.
—  Wikipedia
Everything is morphing together

I still think Arwel’s picture just shows two parts of the set randomly being placed next to each other without any further purpose. (The question is though, why they take down the set already). But what made Arwel choose the word “morphing”?

Maybe this would be giving away too much, but…

Most of us think, looking at the given clues, that ep 4.2 is an adaption of The Dying Detective. In this story Holmes locks himself in his bedroom. pretending to be seriously ill, and sends John to solve the case. We’ve seen Sherlock wandering through London, but he seemed a bit off. Somehow intoxicated, poisoned? I wondered, if he were halluzinating instead of deducing. 

So maybe, what’s morphing is 221 B. Sherlock doesn’t lock himself physically in 221b this time, but he’s locked there inside his mind. Everywhere he goes, the real world starts morphing into 221B. He may be unable to talk to people, to see what’s going on. All he can see are the walls of 221b and he can’t get out.