She remembers when she first met him. He had been standing by the dock and she remembers thinking that she had never seen such a sad 10 year old before. That's when Isabelle Lightwood decided that she was going to make that boy smile.

i. She was eleven when she stepped outside to rescue Church from the rain and had found him soaking wet on the Institutes stairs. Even through the rain, she could see that he had been crying. She'd placed her hand in his and led him into the front garden. She put his hand on her waist and hers on his shoulder and just as she started to lead him in a waltz she'd murmured:

"Would you, could you, in the rain"?

So they danced and she told him jokes and stories that made him laugh and by the time they entered the Institute they were sopping wet and laughing at each other's imitations of Maryse when she found out what they had done.
It's safe to say that Church was never rescued.

ii. She was twelve when she got her first Mark and she remembers clenching her teeth in an effort not to cry, as rain poured outside. The burns from her very first Mark had hurt a lot and she was sobbing in the library when he found her. She didn't turn away when he caught her crying, she figured they were even now. He had walked across the room to where she was sitting and held her while she clutched his T-shirt and sniffled on his shoulder. She showed him her burns but she started to pull away when he pulled a stele out from his pocket. He brought her back and whispered:

"Would you, could you, in the rain"?

So she let him draw a rune on her burns and instead of the pain of earlier, it was a soothing feeling. He looked down at her and said, "It's an Iratze – it heals Nephilim". She looked up at him and that's when she realised that she might just love Jace Wayland.

iii. She was standing in the doorway watching him play the piano. It was beautiful and the lightening outside seemed to blend with the melody. She went to step inside when he noticed another person in the room. He stopped playing and just looked at her. She shivered at the intensity of his amber gaze.
" Keep playing, it was beautiful".
He seemed to be considering his options when he said "Only if you play with me". She thought he had been joking but he got up and grabbed her hand and steered her towards the piano. She sat down and he slid in beside her, "I don't know how to play" she confessed.

"Would you, could you, in the rain"?

He took her hand and place his own over it and he gently began to lead her in a symphony of sounds. She smiled as she got the hang of it and he laughed as she began to make up her own music.

iv. They were watching a movie and she had her feet in his lap and was tracing the rain drops on the window next to her. He shifted and turned towards her with a grin on his face, "If you didn't want to watch the movie, you could've just said so".
She'd turned towards him with a sarcastic comment on her lips only to have her throat seize up as she realised just how close his face was to hers. He was staring at her lips and just as he leaned forward she breathed:

"Would you, could you, in the rain"?

His lips met hers and she wound her fingers in his blondeblonde hair. His hands curled around her legs and he pulled her onto his lap. The rain continued to fall as they kissed and she couldn't imagine anything ever being this perfect. They heard the click-clack of Maryse's heels and broke apart. She threw herself onto the other side of the couch as he smoothed down his hair. The heels click-clacked past and they breathed a sigh of relief. "We can't do this", he said. She looked at him with solemn eyes as she replied "I know".
He kissed her anyway.

v. She's sixteen when she comes to his room at night. He woke up to a long, warm body sliding in next to his. He turns toward her and looks into her ebony eyes as her lips meet his. They're all raging fire and muffled moans because they shouldn't be doing this but they know that they're only themselves when they're together. It's raining that night, and it seems just like fate because it always rains when these moments occur and she wouldn't have it any other way. So they kiss and touch and the sound of droplets hitting the roof creates a rhythm to their movements and just as their hips come together she whispers in his ear:

"Would you, could you, in the rain"?

Afterwards, she curls up next to him and drifts into sleep, timing his breaths with hers. She thinks that her first time couldn't have been better and that everything in the world is perfect. They wake up together and are greeted by a look of bewilderment on Alec's face. She's only half-listening when Jace spins a story about nightmares and shadows because she's just realised that they can never be together. They're adopted siblings for gods-sake and really she should've known. Alec's accepted the lie and walked off, and she turns to look at him. He sees her eyes water and pulls her to his chest. He strokes her hair and asks her what's wrong and all she can say is, "We can never be together can we". He's quick with his protests and it makes her feel better.
She doesn't believe him though.

In the end she was right. They could never be a real couple. She sends him off with Clary to avoid the suspicious glances that Alec likes to send her way. But every time it rains they'll both make an excuse to be with each other because it's what they do.

It's when she's 26 (she's surprised she's survived that long), that she gets speared by a demon, whose claws were dripping with venom and black ichor. She lies watching as Alec stands there white as a sheet while Jace is frantic with his efforts to keep her alive. It won't do anything, she knows that but it makes her smile because after all this time, he still loves her. She's slipping into the darkness but she's determined to do this. She gazes into those amber orbs and mouths:

"Would you, could you, in the rain"?

He has tears in his eyes as he leans down and kisses her. And he wishes they could've had something more than meetings in the rain but they've run out of time and he's grateful for this chance.
He breaks it off with Clary and she doesn't really mind because now everyone knows about them and he knows they only accepted it because she's gonegonegone. But every time it rains, he'll stand at a window and think of her, until the rain stops. He knows that she's there somewhere because the droplets on the window form a pattern and this pattern always makes him smile,

"Would you, could you, in the rain"?