Quick Answer: The title of the Season 2 premiere episode comes from 1 Corinthians 13:12 (King James Version), “For now we see through a glass, darkly; but then face to face: now I know in part; but then shall I know as also I am known.” The title invokes the metaphor of seeing one's reflection in a mirror to represent Claire's confused identity and her desire to unify a self that has been divided into two fragments in separate times and between two different men.
Outlander (2014 - ) all about the "then" vs the "now," the past and the future. Juggling the two is handled, as is expected in a time-travel story, in a non-linear fashion. Claire's (Catriona Balfe) "now" always has a "then." Her past is often in the future. The dichotomy of the two halves of the Outlander universe provide challenges and exciting opportunities for the Starz’ adaptation: how to maintain the tension and suspense of the now when the weight of history and the future (or past) are always looming large.
[Beware: Wee spoilers ahead for Season 2, Episode 1: “Through A Glass, Darkly.”]
The episode title comes from a famous Bible verse. Paul wrote in 1 Corinthians 13:12 (King James Version), “For now we see through a glass, darkly; but then face to face: now I know in part; but then shall I know even as also I am known.”
Within this Bible passage (which is a favorite reading choice for wedding ceremonies for its focus on the overriding importance of love), the “glass” is a mirror. The New International Version translates the lines, "For now we see only a reflection as in a mirror; then we shall see face to face. Now I know in part; then I shall know fully, even as I am fully known." Paul is talking about seeing an imperfect version of yourself or your reality.
(This concept of an imperfect reality is a popular one amongst writers, poets, and filmmakers. Several episodes of television feature the same title, including one from a different Scottish time traveling tale: S4E18 of Highlander (1992-1998)).
Claire will always be out-of-time no matter where (or when and maybe who) she is, whether we are set in the 18th century or 1948, which is when the episode opens. Starting Season 2 in the 1940s with her first (non-chronologically in time but chronologically in the story) husband, Frank Randall, would be more jarring if not for the break between the seasons. (For viewers watching the final episode and then immediately starting the next season this will be a bigger problem.) The finale of the first season ends with Claire and Jamie leaving Scotland on a boat headed towards France and Claire telling him she’s pregnant. It is a hopeful ending to a horrifically bleak series of episodes that comes to a full stop with the time jump to 1948.
The first half of the Season 2 premiere episode is spent here in 1948. This is a challenging choice because the narrative heart of the story doesn’t beat between Claire and Frank, but between Claire and Jamie. On the other hand, there is an interesting conflict at play over what Frank can and will believe of what Claire tells him as he questions who this person is that has returned to him after a three-year disappearance but is a diversion from the forward motion of the series. Here, it is evident that Claire knows she has made a choice (even though viewers don’t yet know the motivation behind this choice) to return and that she is facing a future with an inauthentic version of herself. She sees the dark shadow of herself in the mirror. This is an important story note for Claire, but spending an entire half episode on this point is still a bold choice.
While in this first half the "Through a Glass, Darkly" title relates Claire's internal identity confusion, the second half relates to the fragmentation of self in a world that requires us to play many outward roles. This portion of the episode transitions back (forward?) to the 18th Century, and viewers see Claire and Jamie arrive in Le Havre, France. Claire and Jamie are facing the future with a new dynamic as a married couple in a greatly altered reality: Jamie is dealing with the trauma of his rape and torture, and the two face a future (past) as parents. They are also moving from the wilds of the Scottish Highlands to the wild French port town of Le Havre. They must shed their prior selves, or perhaps cloak them in layers of a heightened, false self. As they are trying to convince Jamie’s uncle to provide introductions to the French court and the Bonnie Prince, they must project the personas of passionate Jacobites, a performance exactly opposed to their ultimate goal to stop the rebellion. This need to obscure one's true self in a limited, false representation also invokes Paul's promise of a future in which we are known in full, compared to a present in which we know ourselves only in part.
The episode feels more like two separate pieces rather than a cohesive whole, but that may be the point. Claire, in both versions and times, is struggling with identity and reflection. What remains to be resolved (for many episodes yet) is whether Claire will ever realize Paul's promise of knowing oneself, and being known, with true, uninterrupted sight. Claire's journey is, fundamentally, the search to unify a self that has been mysteriously and unnaturally splintered into fragments.
In the meantime, the contrast between the two periods and places heightens that struggle for viewers, as we all peer into the glass, darkly.