The film begins with a prayer to Odin and ends with a prayer to God. Both are answered in their own ambiguous way. This being Bergman, the wronged father begins by procaming how he cannot understand a Creator that allows such evil to befall a good man. But rather than let that condemnation ring out into silence, he leans once again on the Christian imperatives of sin and redemption. And God listens: a stream appears from out of nowhere to baptise the father anew and wash away the step-sister's guilt. It's a more optimistic ending than Bergman will allow himself down the line.
And what of Odin in the beginning: the lusty, dangerous old man in the forest? He also answers prayers, or fulfills curses at least. The potency of the old gods may suggest that religions come and go, but evil and our attempts to deal with it are perennial concerns, both in the 13th century and in 1960. Then there is the title: the journey from innoccence to experience (sexual and moral) superimposed onto the changing of the seasons. The spring is that liminal time between bountiful summer and cruel winter, and the film's setting seems to move between all three. Evil, like weather, is both immutable and unpredictable.
Thankfully, Bergman's existentialist obsessions do not overshadow his real talent for intimate family drama, particularly in portraying the relationship between the sisters. Karin is already sliding towards corruption (dresses, dances and boys), yet her angelic countenance make her the favourite of the family. They also make her dark-haired (and pregnant) step-sister jealous. No sign of an expectant father appears. Did her lover abandon her, or maybe she was raped as well? We don't know, because any anger she may feel is not directed at the true source of her predicament, but serves as fuel for a murderous resentment against the perfect woman she can no longer be. Her confession before her father is the film's most powerful moment – far more so than the miracle with which it ends.