Building a narrative or vamping for cover?

Daniel Menaker is taking a risk - and I'm wondering if it will pay off: in the 2nd section of The Treatment he embarks with an entirely new set of characters, a different setting, a different tone, a different narrative voice. Why would he do this? This book is not a collection of stories or of 4 novellas; it's a novel, and he clearly wants this work to have a narrative arc, a coherent design. And yet... the second section abandons everything that seemed to be carrying this novel forward, everything that got it attention, the very reason we're reading it. The first section, in which Jake Singer ruins one relationship and then, by (his) good fortune, begins another as a very beautiful, sexy, wealthy, widowed mother of one of the students in his school practically, almost literally, throws herself at him - good for him, he's a very lucky guy - but that's not much of a story, no, the reason the first section is interesting at all - and it generally is interesting - is the counterpoint, Singer's sessions with his intelligent if eccentric analyst, Morales, whose voice and advice and cajoling Singer gradually internalizes, enabling him, at last, to feel happy and confident. Then in the second section we're in the Berkshires with a young woman who goes through several tragic relationships and has a child whom she gives up for adoption - it doesn't take long before we realize that the child is one of the 2 adopted children of Singer's new girlfriend. So these sections will tie together - but at great risk: Menaker is abandoning the most important voice of the novel, Morales's; and his second section narrative is entirely flat as narration - the whole thing (so far, 20 pages or so into it) told as back story, not as surface narrative: the prose feels "mailed in," and it seems as if we're learning all this material not in and for itself but to see, at some point farther down the narrative track, how this woman and her child or children affect the life of the novel's primary narrator, Singer. What I suspect, what I fear, is that Menaker realized he had painted himself into a narrative corner with Morales - he'd created a great character and a great dynamic and really had no idea how to sustain it, and now he's vamping for cover.