I hear an engine roar to life, the purr of a motor as I round the side of the gas station and see Duet doing a happy dance near the open hood. She waves to me when she spots me, running forward lightly, though her body moves like a machine, to grasp my hands in hers, one warm skin, the other hot metal, and pulls me toward the SUV.

"Working now," she says with a huge grin to which her steel half has already adjusted. She's been smiling for a while.

I find myself frowning ...