Let's get right to it, shall we?
First, I give Johns props for addressing the elephant in the room that has dogged the "New 52!" for its entire existence, i.e., DC's insistence that no one got any younger. Anyone reading a "Batman" comic knew that it just couldn't be true: Commissioner Gordon was suddenly in his 40s, Bruce seemed to be Dick's age, Dick seemed to be Jason's age, and down the line. (Re-reading my review of "Batman" #1, it's actually the first thing that I noticed.) Here, Johns acknowledges what we, the reader, always knew: we were missing a good decade in the DCnU.
Wally West -- our narrator -- informs us that a mystery villain stole this decade the minute that the Flashpoint happened. It's a major revelation, because it changes the origin story of the "New 52!" Previously, we believed that the DCnU was different because Barry Allen couldn't return the genie fully to its bottle after the events of "Flashpoint:" he corrected a lot of the changes that his actions in the past caused, but he couldn't correct everything. Here, we're told that it wasn't that Barry couldn't fix everything: it was that someone actively prevented him from doing so. (Barry raises an eyebrow to this assertion, pointedly asking Wally if he's sure that it isn't all Barry's fault. I giggled. I'm still not necessarily convinced either, but I'm willing to go with it.)
This drama of this issue comes from a time-displaced Wally fighting against the pull of the Speed Force as he tries to convey this information to someone in the DCnU. Initially, he's trying to find his lost love, Linda Park, his usual lightning rod whenever he's lost in the Speed Force. But, he can't locate her, so he appears before Batman and then Johnny Thunder. But, they don't remember the DCU, so they don't remember him. At this stage, he begins to lose control over his appearances in the DCnU, and he randomly witnesses Aquaman proposing to Mera. The good (if convenient) news is that this reminder of love allows him to find Linda. However, she also doesn't remember him, and he becomes lost in the Speed Force without her as his anchor. He summons his strength to appear before Barry one last time, to thank him and tell him that he loves him. As the Speed Force is ready to claim him, Barry grabs his arm, remembering him and thus saving him. It's an emotional moment. I teared up a bit, because I really thought that Johns was going to sacrifice Wally to make his point here. I don't know Wally from Adam, but I know that a lot of long-time readers of DC Comics have been clamoring for his return for years. I thought Johns was only going to give them closure, with his death: I'm thrilled to see that he's returned, because it's going to make "Titans" all the better.
The interesting part is that this issue pretty much ends there. I had figured that we'd have the DCU reassembled at the end of this issue, but, instead, the only real development is that Wally returns. Moreover, Johns makes it clear that it's not going to be easy to solve the mystery, because Wally's memories of the DCU immediately begin to fade as he enters the DCnU, just as Flash's did at the end of "Flashpoint." Johns reveals only to the reader that it appears to be Dr. Manhattan, from "Watchmen," that stole the decade, though even here Johns is coy: we don't even directly see Manhattan, so we certainly aren't given any insight into his motives. (Earlier, he appears to kill Pandora, whose absence I think I noted in a recent review. But, we have no idea what connection Pandora had to him or why he had to kill her.) The only hint that anyone in the DCnU has that he's involved is that Bruce is drawn to discover the Comedian's bloodstained smiley-face pin hidden in the Batcave. But, we're given no more additional information, like how it got there or how Bruce suddenly knew that it was there.
Moreover, Johns intersperses hints of future plots in the DCnU throughout the issue, seemingly making it clear that the DCnU isn't going to suddenly end. Bruce is monitoring the fact that two Jokers appear simultaneously and wondering how it connects to Mobius' chair telling him that three Jokers existed. Saturn Girl (I think) has come to the present, though we don't know why. The Atom has discovered the Microverse while exploring a "disruption deep within the temporal nanostructure of the time line," though it's unclear if this disruption is connected to Dr. Manhattan. A cloaked figure called Mr. Oz tells a time-displaced Superman that he and the fallen Superman aren't the people that they think they are. The two new costumed characters that we know will challenge Bruce in Gotham in the pages of "Batman" appear in the shadows. Moreover, newer versions of old heroes appear: a young Blue Beetle, a gay Aqualad, Jessica Cruz as a Green Lantern, a new Kid Flash. But, we have no idea how any of these plots tie into the larger story. How long does the DCnU have? Will the answers to some of these questions be revealed after the DCU is presumably restored? Johns plays his cards close to the vest on all these questions.
In other words, to use the cliché, this issue raises more questions than it answers. The DC Universe isn't reborn in this issue; it just seems to start the process of getting reborn. (It makes the relaunches of the series even more gimmicky than usual.) If I had to guess, we're probably looking at some huge cross-over event next summer. I don't necessarily mind that, though, since it gives Johns the time to get it right. But, we're on shaky ground right now. Readers of Marvel Comics had a similar experience this past year, where we knew "Secret Wars" was going to change the status quo, so it was hard to invest in the stories that creators were telling as the event neared. A year is a long time to wait to see the hints in this issue revealed, so hopefully Johns will dole out more hints to keep us engaged as he goes.