This may be way off, but just walk with me here.
Could the whole "balance" boat ride thing, basically most of the last episode, have just been inside Marc's personality's mind? For an analogy to a movie, it's like going two levels deep in Inception.
Like there's two layers of false realities.
Inside the body there's two personalities, Marc and X.
Marc is then further split into Marc and Stephen. So what we saw last episode was the merging of Marc and Stephen. That was the boat analogy, that personality being "balanced," etc. All that happened two levels down.
But up a level, talking to Harrow in the psych ward, there's still Marc and X. Which is why in this episode we keep seeing Marc go between talking to Harrow and talking to Stephen, and then at one point when the flip happens it's Stephen. At various points, on that level, Marc, Stephen, AND X all talked to Harrow.
To get back to actual reality, he's going to have to deal with X next episode?