Burn care is an intricate and multistep process. Doctors must not only heal the wounds with skin grafts and surgeries, but also keep the body in balance as it recovers. From the moment burn victims arrive at the hospital, they are hooked up to intravenous fluids. That is because the immune system responds to charred skin as a foreign invader — “like it’s a splinter,” Dr. Greenhalgh said. The surge of inflammation puts the rest of the body at risk of dehydration, in a sense, from the inside out.

Skin from Mr. Blevins’s hip was grafted onto his hands. For some with large burns, artificial or donor skin, which the hospital keeps frozen in a bank, must be used as a temporary patch until the body can grow enough skin of its own for the graft.

Throughout recovery, patients are frequently connected to feeding tubes because their metabolism kicks into high gear: Even lying in hospital beds, patients burn calories about 1.5 times as fast, according to Dr. Greenhalgh, as the body goes into overdrive trying to repair itself. Mr. Blevins was released on Nov. 15, but returned Nov. 29 after infection set in, forcing amputation.

Stroking Mr. Blevins’s hair as he lay on the bed in their home, his swaddled hands propped on pillows, Ms. Sykes described how he had saved her from a life of methamphetamine addiction, bringing her from Yakima, Wash., to California about five years ago for a cleaner life. Both are recovering addicts, replacing drugs with the joy of motorcycling side by side. Now they fear that the narcotics Mr. Blevins has been prescribed for pain could send them spiraling. “The last thing I want to do is come in as a burn patient, and leave as a heroin addict,” Mr. Blevins said.

Mr. Blevins’s jobs as an alarm technician and a home health care provider took the couple from living in a car in 2014, to the little creeper-covered home they share with five cats and three dogs in Los Molinos, about 45 minutes’ drive northwest from Paradise. They now fear they will lose it. Unlike residents of the fire site, they are ineligible for much of the federal and state aid pouring into the area, because their house did not burn down.

Then there are the nightmares.

Days revolve around mitigating Mr. Blevins’s anxiety — a scented candle his fiancée lit set off a panic attack, he said — and his twice-daily bandage changes. It is a painstaking process that takes nearly three hours as Ms. Sykes cuts away gauze, removes dead tissue and rebandages each finger.

A few days before his amputation surgery, Mr. Blevins said that in some ways, he felt blessed. News reports of his condition led to a reunion with estranged family members, he said, and his bond with Ms. Sykes has deepened. Others, he knows, have lost far more.

“I pray to God that the families that have lost will heal,” Mr. Blevins said. “The same way I have got to heal physically, they have to heal emotionally.”