Dr. Karl Rosarius, who was known as Charly, picked up his wife, Bettina, at the Cologne train station in Germany on the morning of Dec. 8, 2023; she had just flown in from New York carrying photos of their daughter Clara taken at a Händel concert she had participated in a few days earlier.

That night, during a performance of J.S. Bach’s Christmas Oratorio at the Kölner Philharmonie, Cologne’s main concert hall, Charly suffered a sudden cardiac arrest and died.

“He could not have chosen a better place to pass away,” Bettina said, “listening to Bach in this peaceful place.” Charly was 85.

“It remains a big shock to us all,” Bettina said, “as he was so active, present, and fit to the last moment, and we had planned so many years to still spend together.”

Born in Cologne on March 7, 1938, Charly was the son of Lotte Rosarius and Dr. Alois Rosarius, a surgeon who practiced in Cologne, where Charly grew up. Charly’s mother took him and his older sister to Bavaria for the duration of World War II while his father remained in Cologne to continue his medical work.

Poet Suzanne McConnell noted in a tribute that “because of the war, Charly found it difficult to leave food on a plate. I recall his anecdote about a neighbor who traded an expensive Persian rug for a bag of potatoes.”

The family was reunited in Cologne after the war.

Charly left Cologne after graduating from gymnasium to study medicine at the Albert-Ludwigs-Universität Freiburg. During his years there, he learned to ski, and his friends introduced him to classical music and contemporary art. His extensive engagement with art was captured in a 2019 Art Blog Cologne interview, in which he discussed the works of Cy Twombly and Claes Oldenberg, among others; the entry noted that Charly started collecting art as a student.

He received his Ph.D. in medicine in 1964, and after practicing at several hospitals, Charly elected to specialize in radiology.

In 1974, Charly founded with a partner an innovative radiology practice called Gemeinschaftspraxis für Radiologie und Nuklearmedizin (Community Practice for Radiology and Nuclear Medicine). They invested in the latest technologies, becoming a large institute with several partners and many employees by the time he retired in 2006. Charly was the first to acquire a PET (positron emission tomography) machine in Cologne, years before other hospitals and institutes followed suit.

Charly visited Cape Cod for the first time in the late 1970s, renting an old house on Longnook Road in Truro with some American friends. He fell in love with the Outer Cape, and some five years later, following the lead of two of his close friends from his university days, Frika and Heidi Klöck, bought a summer cottage on a kettle pond in Truro.

Charly was fascinated by “the quietness of the woods, where he would hike for miles, the beauty of the light, the swimming in ponds and the ocean, the untouched nature, the lack of elegance, and the luxury,” Bettina wrote in an email. Charly used to say that “the luxury lies in the peacefulness, the emptiness and quietness, something you rarely find nowadays,” she added.

Back in Cologne in the early 1990s, Charly was introduced by friends to Bettina at the opening of the Museum Ludwig. Their friendship developed through their shared interest in the arts.

“We got together in late 1996, after our marriages broke,” Bettina said. In 1997, they spent their first summer together at Charly’s kettle pond cottage.

Bettina was introduced to the Outer Cape in 1996, and, like Charly, she fell in love, finding peace and restoration in a six-week stay with her daughter. “It was just like heaven,” she said.

Charly and Bettina married in Cologne in 2000, and with Charly’s three boys, Bettina’s daughter, and their daughter Clara, born in 2001, they spent summers here with friends from Germany, Boston, and New York and year-rounders.

Charly embraced simple things in his Cape summers. He practiced carpentry, something he never did in Germany, and built outdoor furniture for the cottage and shelves for his daughter’s books, “her happiest piece of furniture,” Bettina said.

Charly loved family evenings by the bay and enjoyed singing songs around a fire on the beach at night. He organized community breakfasts with his German and American friends featuring blueberry pancakes, coffee, and fruit, and he learned how to shuck oysters.

“He was no fisherman,” Bettina said, “but he loved to eat fish.”

An American friend, sculptor Gary Kuehn, recalled in a tribute the more than 30 years of annual gatherings on the Cape; there would be “sundown gatherings at Bound Brook Island and dinners together at one house or another.” Charly helped Kuehn archive some 3,500 of his works, a project, Kuehn wrote, that “gave me a new way of thinking of my life, a clear sense of the often-unconscious focus of my identity as an artist.”

Charly’s knowledge of music and literature was comprehensive, and he loved to share it with anyone interested.

“His heart belonged to classical music,” Bettina said, “and he knew the birth and death dates of every composer.” He admired the work of W.G. Sebald, James Joyce, Max Frisch, and Philip Roth. He wondered, Bettina said, “why John Updike never won the Nobel Prize.”

In 2006, after Charly retired, he and Bettina moved to New York City for a year that turned into 14 years, until Covid hit, at which point they often came to the Cape out of season, usually staying in Provincetown between October and April, where Bettina has run the Gaa Gallery since 2015. They loved the Outer Cape in the off-season almost more than in the summers, with the transparency of the woods, the winter light, and the absence of summer visitors.

“Everyone still alive from the cohort of medical students 60-plus years ago meets once a year for a long weekend in Freiburg to celebrate old times, update and check on everyone, talk and laugh and eat together,” Bettina wrote in an email. Charly and his two oldest friends would drive down to Freiburg together, “excited as students in their 20s, despite being in their 80s. The last time was early November 2023.”

Charly is survived by his wife, Bettina Rosarius, of Cologne and New York, and by five children: Leo Rosarius of Cologne, Alexandra Hecker of Cologne, Anton Rosarius of Düsseldorf, Oskar Rosarius of Munich, and Clara Rosarius of Ann Arbor, Mich.

His funeral took place on Dec. 20, 2023 at the Reformationkirche in Cologne.

Editor’s note: Because of a reporting error, an earlier version of this article, published in print on Jan. 18, incorrectly stated that Bettina Rosarius first came to the Outer Cape in the early 1980s. It was in 1996.