Her

AU where Sherlock never met Molly. Mycroft was the one who helped him survive the fall. Now he's back, but things have changed. John's married, and Sherlock's had issues dealing with his loneliness. Mycroft's come up with a solution, a new program based on AI. What happens when the man who is known as a machine. . . starts to care for the machine? What if she isn't just a machine?