Cas reaches a hand out and murmurs something to the jellyfish in the aquarium, like he and the creatures within are old friends. Sam doesn’t know if she’ll ever feel that kind of bone-deep familiarity with something that seems so unfathomable. No brain, no lungs, no heart, and yet the jellyfish are here, beautiful and pulsing in front of the two of them.
There are times Sam wants to take out her brain and scrape the mold off, to turn her lungs upside down and shake out all the ash, to plunge their heart into a pot of boiling water until it resurfaces with all of its tainted blood washed away. There are times Sam feels the depth of her uncleanness down to her bones, down to her soul.
Cas turns away from the jellyfish to look at Sam. The blue light from the tank highlights the way his brow furrows in concern.
Cas doesn’t have a soul, and he doesn’t need his brain or lungs or heart to live. Sometimes, he - and everyone else - feels too far away to touch. Sam remembers watching, in a medical show, blood being pumped out of someone, filtered through a pig’s- was it a liver?, and coming back in clean. It’s something they used to wonder about while lying in bed, pretending to sleep because Cas wouldn’t. if they could send their entire self through Cas and come back clean. The thought is less pressing nowadays, though - Sam can feel the sun on her skin and call it hers, she can sleep without nightmares. They have therapy, a new job. She’s working on it.
“What are you thinking about?” Cas-in-the-present asks Sam. Sam tells him. By now, it’s nothing new. “I’m sorry,” Cas replies, as he always does, and threads his fingers in Sam’s. “Do you want to look at the seahorses instead?” She squeezes Cas’s hand tighter and nods, and they make their way over to the next tank. Sam waves at the jellyfish as they go. One day, Sam hopes to greet them with the same amount of gratitude she uses when she says goodbye.
The day their betta fish falls ill, Cas's first thought is that he has to kill it, bury the body, and leave town. Then, the guilt sets in. This is because of him, he knows it, every time he hadn't been able to muster the will to feed it on his days and every time he'd forgotten to check the pH of the water. Schedules and stability are difficult. Time is like syrup to him, drips of memories between spaces rendered empty by Naomi or his few months in a human brain, hours sometimes feeling like milliseconds or sometimes like millennia.
Sam finds him half a millennia later, still crouching and staring through the tank at Bluebell's patchy scales and sluggish movements. Some days, Sam is Cas's only timekeeper. Other days, Cas looks at Sam and can only see the cracks that he's responsible for. "This is my fault," Cas whispers. He means, please forgive me. Sam frowns. Then, they ask, "Have you tried healing her yet?" The stale breath in Cas's lungs punches out in a single sharp laugh. "N-no," he murmurs, and knows he sounds ridiculous, "no, I didn't... I hadn't thought of that." He reaches into the tank, feeling his grace flow into Bluebell. A few seconds pass, and then she swims away vigorously.
"I'll clean the tank today," Sam tells Cas, rubbing his shoulder reassuringly. "She's my responsibility too."