Sean Plummer has spent the past few weeks surrounded by the love and laughter of teenagers, who gathered at her Angels Camp home every day since news broke of her children's tragic deaths.
The murders of Alex and Macaila Marshall, both Bret Harte High School students, stunned a quiet community and was the first experience of loss for many of their young friends.
But Plummer, who prefers to be called simply "Seanie," said she and the students are helping each other heal by remembering her children's zest for life.
"They were just pure light," she said in a recent Union Democrat interview. "It doesn't get any better than them. I called them my helium. They filled me up."
Alex, 17, was a junior. Macaila, 14, was a freshman.
The siblings and Plummer's dog were shot at some point around Jan. 31 by their father, Philip Marshall, who also killed himself, according to the Calaveras County Sheriff's Office.
Plummer was Marshall's wife. They separated from him in 2008 and filed for divorce last fall. She was in Turkey on a business trip at the time of the killings. She is changing her legal name back to Plummer, her maiden name.
She said she isn't ready to talk publicly about Marshall. At some point, she said, she plans to address questions related to mental illness and gun control.
"That's the next chapter," said her close friend Sandra Fischman, of Lafayette, whom Alex and Macaila knew as an aunt and whose two children grew up with them.
Since their deaths, Bret Harte students have written Alex and Macaila so many letters that they could be bound together into a book with more pages than "Moby Dick."
Plummer estimated that 20 to 30 teenagers have slept at her Angels Camp home every night since she returned from Turkey, crammed together in a downstairs room she called "The Cave."
That wasn't so different from the state of things during Alex and Macaila's lives, when at least 10 friends would sleep over each weekend.
At a Feb. 9 memorial service for the teens at Bret Harte, Plummer gave a speech credited by some parents for helping students start the healing process.
"That wasn't me - that was Alex and Macaila," she said.
The night before the service, she took a group photo of students in her living room mimicking the siblings' goofy poses. For Alex, that consisted of hands drawn back like the comic book hero Spiderman before he releases webs.
"I'd hear them laughing and crying and playing videos," Plummer said of the teens who gathered at her house. "Just grieving how grieving should be … in the purest form of every emotion. Just remembering."
The students drive to her home during lunch breaks and after school, checking up on her. On Friday, she had Valentine "dates" with two girls and Alex's friends, going on a scavenger hunt to his favorite places - which included Starbucks and a movie theater.
The walls of her house are decorated with photographic tributes to the siblings.
She said she was their "personal paparazzi" and took "millions" of photos of them throughout the years, from pictures of Macaila wearing a pink dress and a crown of flowers to Alex in one of his many Spiderman costumes.
She even captured Alex's first Valentine's Day date with a telephoto lens. The sixth grader had made his own reservations at the Murphys restaurant Grounds and painted his shoes red in honor of the occasion - the "cutest thing ever."
Though their lives were cut far too short, Plummer paints a portrait of Alex and Macaila so vivid that their presence can be felt in the room.
They grew up in Murphys, Santa Barbara and Vero Beach, Fla. They were close to their older sisters, Plummer's children Cortnie Alter, 31, and Brittany Alter, 29.
"They were kind of like their little mamas," she said. Macaila would call Cortnie every night to "download the drama" and chat about TV shows they watched, which included reality shows such as "The Bachelor."
Alex and Macaila were there for friends, a shoulder to cry on.
Though a gentleman, Alex was constantly giving hugs.
"That was his gift," Plummer said. "He made every single person feel like they were the only person in the world."
When she complimented him on his handsomeness, he playfully responded that he was already aware of that fact.
His love of Spiderman began when he was small, probably, his mom said, because the comic book superhero used his power to help people.
He even started a secret page devoted to Spiderman on the social media site Pinterest.
After high school, he wanted to become a pilot.
Macaila had an uncanny knack for being at the right place at the right time.
In Las Vegas a few years ago, she met the then-newly elected President Obama and did a "soul handshake" with him, Plummer said.
Among her other acquaintances were the mayor of New Orleans and film director James Cameron, whose credits include the 1997 blockbuster "Titanic."
She wanted to study at the Brooks Institute of Photography in Santa Barbara, inheriting her mother's interest.
The two were "always behind that lens," Fischman said.
Macaila's childhood was spent setting up elaborate Barbie dolltowns with her friends, dressing up for her Audrey Hepburn-themed birthday party when she turned 10, and leaving a deep impression with her generous spirit.
In second or third grade, Macaila decided to donate about $13 in gift money to a children's hospital. While living in Florida, she and Alex set up a lemonade stand and raised $750 for the family of a child killed in a drive-by shooting.
Defying stereotypes about teenagers being ungrateful, the siblings expressed thanks to their mother on a regular basis.
"This is the letter where I thank you for all you have done for me, and boy is that a lot!" Macaila said in a Christmas note to her mom. "I think you are the best mom out there even though you deny it!
"I love you mommy," the note finished.
Plummer had saved every one of Alex's Halloween costumes. She kept every bit of baby clothing, every pair of shoes, and other mementos of the siblings, right down to their umbilical cords.
"I'm so glad I did," she said.
This year the siblings were supposed to start traveling internationally with their mother, who owns a shopping business. She said she will carry some of their ashes, along with her dog Sukie's, in jewelry so they can see the world through her eyes.
She said every time she starts thinking about the nature of their deaths, she shifts her attention back to their happy lives instead.
"They're just reassuring me to look up," Plummer said. "The 'whys' don't matter. There will never be an answer good enough. Ever."
Plummer is moving to Carpinteria near Santa Barbara in the near future.
But, she said, she plans to buy bunk beds and trundle beds so Alex and Macaila's friends can continue to visit her.
"They've been here for me, and I hope I've been there for them," she said. "They're my babies, all of them … it doesn't matter what time of the day or night. They know they can just have a place to hang out.
"The bottom line is these kids have healed me," she said.