Just a day after Christopher Evan Welch landed a career-making role on HBO’s “Silicon Valley,” he received some heartbreaking news. The lung cancer he’d been battling successfully since the fall of 2010 had spread to his brain.

Chris was sitting with his wife, Emma, and his doctor at Memorial Sloan Kettering in New York. “I have to go shoot this pilot,” he said, stunned.

Welch was 47. Before his diagnosis, he’d been a fanatical cyclist, winging around Central Park on his fixed-gear bike, his thin brown hair flying behind him. Nobody could say why the cancer had attacked his lungs, then his prostate, and now his brain. He was a casual smoker, and he enjoyed the occasional steak at Keens, but so did lots of people. Maybe the weeks Chris spent after the 9/11 attacks helping out at ground zero were a factor. Or maybe it was all just the result of some horrible mutation that lay dormant in his DNA all along.

With aggressive treatment, Chris and the doctors had kept the tumors at bay so far. The latest news was bad, but he and Emma were used to that. One more fight in a grim slog.

It was agreed the surgery could be put off for a month, and Chris went to Los Angeles, where he created the role of comedically awkward, creepily soft-spoken angel investor Peter Gregory.

Based loosely on the slightly less awkward, creepily soft-spoken PayPal cofounder and Facebook angel Peter Thiel, Gregory is a linchpin of the series, funding the startup, Pied Piper, around which the action revolves. More than that, he’s a poster boy for the tech world’s imperiousness, its brilliance, and its odd alienation from the very world it is forever trying to make “a better place,” as one character after another puts it in one of the show’s running gags.

Welch shot five episodes before further complications related to the cancer took his life this past December.

While the show is charming and keenly observed, and will likely thrive even in his absence, watching Peter Gregory, TED-talk Socrates and sesame-seed tycoon, drive his absurdly narrow Smart car off into the Northern California sunset won’t be easy.

Judge has long specialised in wounded, insecure, painfully uncomfortable men (from “Beavis & Butthead” and “King of the Hill” to “Office Space”), and despite Peter Gregory’s brief time on screen, he is already among the most indelible. Amid a cast that often seems like a taxonomy of male social inadequacy, Gregory is the most awkward of them all. Letting his hands dangle helplessly like a neurasthenic T. rex, speaking with an exaggerated formality, he’s a ridiculous, magnetic, and deeply human figure — the irreplaceable heart of the show.

* * *

Lanky and floppy-haired, Welch grew up in Dallas, the oldest child of a Korean War vet and a homemaker. A theatre geek in high school, he attended the University of Dallas on a full scholarship, then went on to grad school in Seattle, where he fronted the Ottoman Bigwigs, a brainy indie-rock band with a small but devoted cult following.

He arrived in New York in 1997, appearing in a revival of Molière’s “Scapin,” opposite neo-vaudevillian Bill Irwin, delivering a slapstick tour de force that The New York Times called “a sensational debut.”

In the years that followed, Welch built up an impressive career as a character actor, one vaguely familiar to anyone paying close attention but, as Vulture rightly noted, maddeningly hard to place. Except for one unhappy attempt to wait tables in Dallas during college, he made his living — modest though it was — exclusively as an actor.

Getty At the opening night party for ‘Romeo & Juliet’ at Shakespeare in the Park

Welch did his share of “Law & Order” episodes, like every New York actor, and was a regular presence off-Broadway and off-off-Broadway. He made it to Broadway a couple times as well, most notably as the tormented Reverend Parris in a 2002 production of “The Crucible,” opposite Laura Linney and Liam Neeson. But he also did plenty of experimental and regional theatre, and it was while appearing in an out-of-town show, a 2005 revival of J.M. Barrie’s “Dear Brutus” in Westport, Conn., that he first met Emma Roberts. “We played husband and wife, and we wound up falling madly in love,” she remembers.

Chris could be snobby about doing commercials, although as an obsessive newspaper reader he was thrilled to land a New York Times ad. He had a great voice. He narrated Woody Allen’s “Vicky Christina Barcelona,” and made decent money reading audiobooks, including the young adult “Last Apprentice” series, “The Imperfectionists,” and John Grisham’s “Playing for Pizza.”

He was a big guy, over six feet, but he exuded vulnerability. His face, hawkish but soft, had something of a permanent wince about it, as if he expected to be smacked at any moment. Even when he played smarmy or sinister, that fearful look around his eyes, that cosmic flinch, made him relatable and drew audiences in.

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He became a regular on AMC’s short-lived spy series “Rubicon” and, especially in recent years, began building an impressive film resume, turning in uniformly stellar work in small roles — in films like “Lincoln,” “The Master,” and “Synecdoche, New York” — the latter two of which co-starred his friend Philip Seymour Hoffman, whose death just two months to the day after Chris’ dealt a further blow to New York’s tightly knit theatre community. In light of the two losses, Welch’s existential barn-burner of a speech in “Synecdoche,” a performance he pulled together with just 24 hours’ notice, is shattering.

* * *

It started with a persistent cough, which led to an X-ray, which led to a CT scan. This was in 2010. A radiologist diagnosed Welch with stage IIIA lung cancer. Emma was six months pregnant.

The doctors wanted to admit him immediately, but Welch was in a play, “The Little Foxes,” at the New York Theatre Workshop, and like most stage actors, he was determined never to miss a performance. Besides, they needed to process the news. “We’re getting out of here and we are both going to drink a glass of wine,” Emma said. “I don’t care if I’m pregnant.”

Welch went onstage later that night. Then, even as he began chemo, he continued the run while spending his days rehearsing for yet another show he’d been offered, “The Coward.” He finished that run as well. Once he even went on after waking up from general anesthesia.

Things kept happening; life marched along.

A few weeks after “The Coward” closed, their daughter, June Harper, was born.

The lung surgery happened not long after that.

Chris’ health was much improved by February 2013 when his agent called to tell him about “Silicon Valley.” The producers wanted him to read for either one of the rival Internet moguls, Gavin Belson or Peter Gregory, and he picked Gregory. Since he had to stay in New York, where he was appearing in an off-Broadway show, “The Madrid,” with Edie Falco, he taped his audition. Chris knew basically nothing about the tech world. Except for an addiction to Words With Friends on his iPhone, he was basically computer illiterate. But out of the blue, he decided to give Peter Gregory an odd vocal inflection. “I’m setting my voice back in this weird way,” he told Emma excitedly. He felt instantly he’d found the character.

Emma Roberts Welch Celebrating his New York stage debut in ‘Scapin’

Chris didn’t know then how right the choice was, but as it happens, Peter Thiel also happens to speak rather haltingly. Chris was offered the role immediately.

The timing was perfect. With the illness, Chris hadn’t been working as much, and money was tight. Suddenly, things were looking up. Every actor dreams of an HBO series. “This was the job that changes the game,” Emma says.

After taping the pilot, Chris underwent surgery to remove the brain tumour, and the operation was declared a success. But then came yet another blow. His blood-cell counts were dropping, and the doctors diagnosed AML, acute myeloid leukemia, most likely brought on by the earlier radiation treatments.

“He was just really unlucky,” Emma says. “So unlucky.”

There was really nothing to do but keep fighting. After a gruelling summer, including six weeks in the hospital and repeated visits to the emergency room, Welch began what seemed like a miraculous recovery. “The lung had been removed and that was the end of it,” Emma recalls. “The brain was fine, the leukemia was in remission, the prostate was under control.” During a physical with a doctor working with the network — a standard requirement for an actor signing on to a TV series — he disclosed his medical history and was declared fit for the job. “You’d be surprised how many people I see who have cancer,” the doctor told him.

“We thought we were home free,” Emma says.

Chris and Emma moved into a rented bungalow in Santa Monica with June, who was then 2. He was in remission and holding steady. They were living near friends, in a great house a few blocks from the beach. Welch was needed on set only a couple of days a week, and the rest of his time he devoted to June, playing elaborate games, telling stories, singing songs, and going to the park.

Things were good. Welch enjoyed being “the old guy” on a set full of young comics, and he was thrilled to discover that one of the show’s producers was Clay Tarver, guitarist for one of his favourite bands, Chavez. Mostly, he loved inventing Peter Gregory. “I’m just locked in,” he said. He even began to fantasize about being nominated for an Emmy.

The work seemed to be contributing to his recovery. He was putting on weight and feeling healthier than he had in a while.

Then, the show took a break for Thanksgiving.

The Sunday after the holiday, Chris suddenly felt awful. He couldn’t get out of bed. He was vomiting, and his blood pressure dipped. There’d been rough days before, though. Nobody panicked. Emma started making calls, first to the ambulance, then to some friends, to come look after June.

“Do I need to make a call to HBO?” she asked.

“I don’t know, maybe,” Chris replied.

* * *

That evening, Chris lay in intensive care with Emma by his side. He was suffering from septic shock. Five hours after heading to the hospital, in the early hours of Dec. 2, his heart gave out.

Emma thinks it may be for the best that Chris died the way he did — so suddenly, during such a high point, without time to brood about what he’d be missing. The last months of his life were idyllic, she said. June missed her dad, of course, but she was just 3. She would be OK. And Chris had written to her in case something happened — letter after letter she could reread when she was old enough.

But Chris was a dedicated performer, and knowing that he wouldn’t be able to finish what he’d started on “Silicon Valley” would have been unbearable in its own way. It was good he was spared that.

Faced with a similar situation, many producers might well have opted to put off a show’s premiere and reshoot a character’s scenes with another actor in the role.

Executive producers Mike Judge and Alan Berg never even considered it. “The brilliance of Chris’ performance is irreplaceable, and inspired us in our writing of the series,” they said in a joint statement. It was bad enough that they had to rewrite subsequent episodes in which Peter Gregory was originally going to appear, reimagining several major story points. “Cutting Chris out of those scripts was among the most difficult things we have ever had to do as writers,” they added. “The entire ordeal was heartbreaking. But we are incredibly grateful to have worked with him in the brief time we had together. Our show and our lives are vastly richer for his having been in them.”

For the series’ viewers, too, the loss will be acutely felt. We won’t have seen nearly enough of Peter Gregory or of Christopher Evan Welch. Then again, it was so nice getting to know them both.

* * *

Emma Roberts Welch was kind enough to share a video their friend Jennifer Kleinman put together for Chris’ memorial service. It’s a beautiful tribute to his life and career.

&amp;amp;lt;div&amp;amp;gt;Please enable Javascript to watch this video&amp;amp;lt;/div&amp;amp;gt; And here, a wonderful track from the Ottoman Bigwigs' self-titled 1996 album, with Chris on vocals. Grieve from Ottoman Bigwigs on Myspace.

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