Here be spoilers.
Charlie McDowell's The Discovery presents itself as a film about the afterlife, but it's more specifically a film about regret. As I touched upon in my review, The Discovery follows three main characters, each of them consumed in some way by regret over a past action they can no longer go back and change, and each of them taking actions that are almost singularly motivated by a desire (and ultimate inability) to cope with that regret.
In the end, the film's events are revealed to have taken place within a memory loop, part of an afterlife that central character Will Harber has graduated to after living his normal life to its fullest and then dying. In a "memory," a version of love interest Isla explains to Will that he has been living within the same loop, and that his ability to finally save Isla from suicide — thereby correcting the regret that most centrally dominated his life — has broken that loop and enabled the both of them to move on. The Discovery posits that the afterlife is an alternate version of our real lives, with the key difference being that we're given the chance to make different choices and correct our most troubling regrets in our do-overs. As such, the film reveals that its events have been one iteration in a continuous loop of Will's afterlife, replaying itself until he's able to save Isla and truly correct his life's biggest regret.
Conceptually, this is an interesting idea, but The Discovery seems fundamentally unaware of the fact that this third-act reveal raises some huge implications that it fails to address in any way whatsoever. One of the most fundamental issues is what happens to people who die without having any serious, towering regrets?
Everybody in The Discovery is miserable as fuck, which is in line with the film's choice to be a meditation on regret. For the most part, it succeeds in this goal, but the script fails to specify what happens to people who don't have this kind of towering sadness in their lives. Not everybody lives with the kind of wracking guilt that the characters in The Discovery all feel, but the film seems to imply that all of humanity trudges along wishing they had done things differently. The implication that the afterlife is a chance to do things differently is mostly presented as a chance to correct mistakes — only the small detail of the dead man's changed tattoo suggests that we might simply want to also try on new clothes. But this detail is the only one of its kind, and is overshadowed by the work the film does to show us that everyone who goes to the afterlife experiences the chance to correct their life's biggest regret when they do so.
Either way, The Discovery takes place well after Will Harber has died. In the film's final moments, he learns that he's been living in a memory loop, starting back at his meeting with Isla every time he fails to keep her from committing suicide. When he is finally able to save her, he is able to move on. The only problem with this is that there are two huge implications here, neither of which are expanded upon. The first implication is that the afterlife repeats itself until you figure out how to actually go about correcting your biggest regret. Doesn't that kind of make it some sort of shitty, torturous puzzle, as opposed to an uplifting second chance that allows you to experience and know what it would be like to have lived a different life? According to The Discovery, when we die, we go to some kind of fucked up Groundhog Day where we relive the same set period of time until we can figure out how to correct our life's biggest regret.
The second implication is that the afterlife is a series of alternate lives, none of them terribly different from the previous one, stretching on into infinity. When Will finally figures out how to correct his biggest regret and leave his Groundhog Day loop, Isla tells him that he will now be able to move on. Immediately following this, it turns out that "moving on" just means going to another alternate version of David's real life, this time one in which he manages to keep Isla's kid from drowning and correct not only his life's biggest regret, but also hers (too bad she didn't get to be responsible for this, I guess). Glossing over the fact that the whole point of this was so that he could reunite with her and fall in love again, but she's got a kid so we're just to assume that she's a single mom...this implies that the afterlife consists of just a repeating set of alternate lives, none of which are ever markedly different from your original life.
If Will's original life involved Isla committing suicide, his first afterlife involves him figuring out how to keep her from committing suicide — the alternate version of his life that allows him to erase his biggest regret. Once he experiences this, he goes to another alternate life, in which he meets Isla under different circumstances and keeps her son from drowning. So are we to assume that he will just continue to hop into a series of alternate versions of his normal life, each with slightly different details, for all of eternity? No way to tell.
Finally, the biggest problem of all is that we have no idea why Will was finally able to move on. This is supposed to be the film's emotional climax: Isla tells him that this time he was able to save her. This time, he was able to connect with Isla in a way that kept her from killing herself, but the problem is that we're not told what Will learned, changed, or did differently in order to enact this change, so we don't understand what will needed to learn to move on. Because Will doesn't really learn anything. In fact, the film implies that Will has already learned what he needed to learn in order to move on, and this last iteration of his loop appears to be the one in which he's finally given the chance to actually apply his knowledge. For the viewer, though, it's hugely unsatisfying to be told this without also learning what it was that Will was doing differently before that wouldn't let him save Isla. That's something I'd like to discover.