When Molly Hooper was introduced to Sherlock Holmes, the first thing she noticed was his opalescent eyes. They were a mix of blue and green with flecks of gold, but they also changed depending on the light, on his mood, and on the colors around him. It was his eyes she fell in love with first, she realized later. The beguiling swirl of colors mirrored his beguiling, multi-faceted personality. Though he claimed to be emotionless, Molly knew anyone who took the time would see exactly what he was feeling in his eyes. As good of an actor as he was, he couldn't hide everything he felt from the world, especially when he was hurting.
Sensitive and fragile, just like opals.
His life, his world was dangerous and she knew it all too well. The way he saw it, keeping everyone at a distance would keep them all from harm. She knew he'd isolate himself forever if it would help those he cared about. While she helped him prepare to fake his own death, she heard him mutter that he must be cursed – cursed with a life that puts his friends in danger, cursed with a heart that felt more deeply than he was prepared for, and cursed with a brain that never let him forget either of those things.
Opals were once thought to be cursed too.
When he came back, he kept everyone closer except her. He still kept her at a distance, but she wondered if that was only because of the diamond on her finger. When the ring was gone, Molly hoped he'd let her in and he did, slowly, hesitantly. Then came Sherrinford and the worst day of her life, but even before she knew the reason for his call, she couldn't hate him for hurting her. When he did come to her and explain, his opal eyes full of painful tears he refused to shed, she told him how she had always loved him and always would. After they made love for the first time, she kissed his eyelids and told him what she loved about his eyes. When he proposed a year to the day later, it was with a blue-green opal surrounded by small diamonds, like his eyes when they sparkled with happy tears.
Mrs. Hudson thinks he chose the ring because I was born in October, but I know the truth.