In the heart of Times Square, a nondescript duffel bag appears, its tag bearing an urgent instruction: "Call the Avengers". This mysterious package sets in motion a chain of events that will challenge Earth's mightiest heroes like never before.
 
Inside, they discover a woman with no identity and no memory. Known only as YN, she possesses skills rivalling the best of the Avengers, yet her origins remain shrouded in mystery. During her medical examination, a startling discovery is made. Under black light, bioluminescent tattoos on her back reveal three names—"Rogers, Romanoff, Stark"—hinting at a connection deeper than anyone could have imagined.
 
As the team works to uncover YN's identity, conflicting memories and theories emerge. Natasha can't shake the feeling that she's encountered YN before, her mind drifting to shadowy training facilities and covert operations from her past. Meanwhile, Tony is rocked by a shocking realization: he believes YN to be his long-lost baby sister—a sibling he's never mentioned before, and who strangely has never appeared in any Stark family photos.
 
Steve finds himself drawn to YN's resilience and the mystery she presents, even as questions about her true loyalties linger. There's something about her presence that seems to affect those around her, though no one can quite put their finger on it.
 
YN's fragmented memories slowly return, revealing a web of manipulation and deceit that threatens not only her chance at redemption but the very foundation of the Avengers team. As shadowy forces continue to pull strings from the darkness, YN must confront her fractured past and face truths that could shatter everything she's come to believe about herself.
 
Torn between the fragments of a past she can't fully remember and the promise of a future with the Avengers, YN faces the ultimate choice: Will she unravel the mystery of her own existence, or will the truth prove too dangerous for everyone involved? The fate of not just YN, but potentially the Avengers themselves, hangs in the balance of her journey to self-discovery.