Grief
The moment Molly heard of his jump, of his suicide, she had been at home feeding her cat, Toby. The phone had rung so she picked it up and all she could hear was John's sobbing. She had clutched her phone tighter to her ear as if that would bring her some control, some reassurance to what was happening. But it was no use. John just kept muttering over and over "He's gone. He's dead." And Molly didn't have to ask who, she knew. He had told her himself only the night before.
Her knees grew weak and she fell to the floor. Her sobs matching Watson's as she held the phone to her face, tears blurring her vision. She had told Sherlock she'd help. Anything he needed she'd do and in return he had assured her, promised her that this would save his life. That she counted and she could save his life.
He hadn't told her what was going on or what his plan was he just asked her to do a few things for him. She thought she was helping. She thought she was saving his life. She didn't know Sherlock could be wrong. With these thoughts spiraling through her head she took a few deep breaths to stop her sobbing.
"John," she said. "I'm coming over." She kept the phone to her ear and stood up, listening to his grief the whole way to 221b Baker Street.
As she faced the door she was suddenly hit with another memory of a different time she had stood there anxiously, nervous at being in his home for a small Christmas gathering. Her frown deepened as she remembered she'd never have the chance to see him again, to hear his calculating deductions, to possibly feel his lips on her cheek once more.
She pushed the door open and walked into the flat John and Sherlock shared. He was just sitting there staring at the chair Sherlock always occupied, crying like a lost child. She put her phone in her pocket and gently took John's phone out of his hands. She sat down next to him the words spilling out of her mouth before she could think about it, "I saw him just last night. I – I was about to go home but there he was in the lab telling me he's not okay, he's going to die. I told him I'd help him, I'd do anything for him but – but I guess it didn't matter. He died anyway." Her voice cracked and broke as she recounted her last meeting with him.
John had stopped crying as he listened, "You saw him?"
She nodded as the tears fell harder, now it was her turn to blubber like a baby. "I- I failed him. It's all my fault." She brought her hands to her face and John pulled her into a hug.
"It's not. It's mine. I should've known. I should've been able to stop him." John brokenly whispered.
Molly wrapped her arms around John's waist and they sat there, clinging to each other both feeling the weight of the death of the world's most brilliant man as their sole responsibility.