After Tapiau finished university, he settled in Paris to become, perhaps unsurprisingly, a dealer of 18th-century antiques. But on Christmas Day of 1999, when he was 37, came the first in a series of misfortunes that would tie him intimately to Château d’Aunoy and foretell its reimagining: A hurricane tore through the city and the surrounding countryside, ravaging the Bois de Boulogne and the park of Versailles. Château d’Aunoy’s grounds became a chaotic tangle of felled trees. The storm turned out to be the first squall of Tapiau’s own tempest; soon after, his mother was diagnosed with cancer. Through her illness, her son oversaw the restoration of the grounds, installing thousands of trees, many of them the same beeches, oaks, hornbeams and maples that had originally thrived there. These years brought a few bright moments for Tapiau (including the birth of his twin daughters), but mostly there was darkness: His mother’s death was followed by the demise of his father a couple of years after he had signed over the chateau to Tapiau in 2007. Around that same time, his marriage fell apart.

Afterward, Tapiau began spending most of his time at Château d’Aunoy. As he contemplated what to do with the seemingly endless space, he turned to Yves Gastou, a gallerist who had helped him furnish his former Parisian apartment — a 19th-century hôtel particulier — from Gastou’s eponymous shop in Saint-Germain-des-Prés. Like Tapiau, the animated Gastou, now 71, had grown up steeped in the 18th century; his father had worked for an auction house. He knew the era’s charms and its limitations. But instead of remaining immersed in the past, Gastou moved omnivorously through the 20th century. His gallery freely mixed periods and cultures: the polished curves of the Italian midcentury master Gio Ponti alongside the simple lines of the contemporary British lighting designer Tom Dixon; the refined elegance of the eccentric architect Carlo Mollino with the industrial edge of the Japanese furniture designer Shiro Kuramata.

GASTOU AND TAPIAU shared a desire to mesh a historic sensibility with contemporary pieces to create a modern sense of the Rococo. One of Tapiau’s first purchases for the home in Paris had been a pair of fluorescent-hued acrylic sculptures by Jean-Claude Farhi; he began to see the world anew when he placed them in front of the 19th-century oak boiserie in his living room.