The simplest dish—toast skagen, or crayfish salad on buttered bread—was at once clean and rich, and no other dish seemed necessary ever again. Josefin and I drank Calvados "smashed" (or muddled) with lime and sugar, and I noted how relaxed the bar scene was, with men in jeans and sweaters instead of the jackets and ties common elsewhere. Formality is very much the Swedish way. I told Josefin that I'd watched almost four hundred Swedes tumble out of an Advent concert at the towering Finska Kyrkan, or Finnish Church, in Gamla Stan; amid four hundred farewells, handshakes, and even bows, not one member of the crowd received a kiss. "I grew up here, and I still have trouble meeting people," she retorted. "It is hard to make friends. Swedes are a little cold on the outside."

I then asked the one question most common among foreigners: "How do Swedes survive six months of darkness a year?" "They leave," she replied. "Otherwise, they go a little crazy."

In winter, Swedes pour out of Sweden, heading to Greece, Italy, Egypt (where Josefin and I had met)—anywhere that fends off seasonal affective disorder. As national policy, six weeks of paid vacation a year is really just a mental-health measure.

But the warm months weren't so easy either, Josefin said. "In summer, people also go crazy, but in a different way." She described being awakened by birdsong—at three in the morning. An hour later, the sun is up—and stays that way till nearly midnight.

Consequently, Swedes are typically exhausted in summer, milking the golden season for all it's worth: leisurely picnics, swims in Stockholm harbor, boating in the archipelago, and forays into the vast evergreen forests—the largest wilderness in Europe begins right on the edge of the capital. In June, when nights are so short that dusk and dawn are said to kiss, the summer solstice is the excuse for an all-night revel.

I asked Josefin if the city she had come back to, after years abroad, was the same one she had fled in her youth. She shook her head no. "The city is changing," she told me. The famously generous social benefits are declining, especially housing subsidies to the middle class. Södermalm, where we sat now, once a bohemia full of artists, radicals, and teachers, has been gentrified. The wealthy—of which Sweden produces a great many—are converting even dingy waterfront districts in the northwest into Richistans, dotted with trendy galleries and restaurants. I had suffered sticker shock in one such entrepôt, Skin Deep, where a pair of Sweden's hip designer denims rang up at a euro-inflated 250 bucks. I gently slid my wallet back into my bakfickan.

On my final morning in Stockholm, I took a ferry across the swirling, complex harbor waters, through channels and estuaries teeming with tidal flows, and landed on Djurgården, a convenient green idyll ringed with some of Stockholm's best museums. I wandered off to the Vasa Museum, a single compelling exhibit built around the remains of a navy flagship that sank on its maiden voyage in 1628. Sweden was at the height of its imperial power then, ruling Scandinavia and large stretches of Germany and Russia, and dominating the Baltic Sea lanes while sending trading ships around the world. The Vasa capsized in a humiliating accident, and has been painstakingly rebuilt from pieces raised from the cold Baltic mud, right down to the crew's decorated ale jars (a vital item, given that Swedish sailors were issued nearly seventeen gallons of beer a month).