Wow, that was a twist! I didn't expect Sylvia to be Black Widow.
I like how you used the word "rigid" to describe Sylvia's body language. It suggests that she is strong and determined, but also cautious. The way she nods her head is also interesting. It's not a simple yes or no, but something more ambiguous.
The last line is the best part. It's a great way to reveal Sylvia's true identity and also add a touch of humor. I love the way you used the phrase "my love" to make it sound like Sylvester is in love with Sylvia, even though he doesn't know who she really is.