Rogers isn't home. It's late (and not raining, incidentally) when she gets to New York, so it could be that he's just sleeping and that's why he doesn't answer when she knocks, but she doubts it.
She knocks twice-protocol says she should knock three times, but she's tired and is fairly confident that he's not going to answer anyway-before pulling out the gadget SHIELD gave her.
Leila knows how to pick a lock, but the tool they gave her is quicker.
Nothing. Leila knows how to listen for signs of life. Footsteps. Movements. Breathing. People are never silent, not really.
They think they are, though, and if you listen closely, you can get a bead on what they're doing before they know that you know that they're there.
And that extra second of reaction time can be crucial. It's saved her life more than once.
That's another thing she'd already learned on her own before SHIELD picked her up, long before. Years and years.
Probably she was doing that analysis longer than she remembers; she's just better at it now.
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