I arrived at my sister Lucía’s house almost two hours earlier than planned because I wanted to help her set up her surprise birthday party.

We had arranged something simple yet elegant: a long table in the garden, white flowers, small candles, and a cake I had personally ordered from her favorite bakery. I had a key because I often looked after her house when she traveled, so I let myself in quietly, picturing her happy reaction when she saw everything later that evening. I left the bags in the kitchen, checked the living room, and began arranging the table. Everything seemed normal—too normal.

Then I heard running water upstairs. At first, I assumed Adrián, Lucía’s husband, was showering before going out to pick up something for the party. I even thought it worked in my favor, since I could continue setting up without interruption. I went upstairs to let him know I had arrived and to ask where they had stored some trays. But before I could knock on the bathroom door, I heard a woman laughing.

It wasn’t my sister.

I knew her voice too well to mistake it.

A sharp pressure hit my chest. I pushed the door open slightly—and everything fell apart. Adrián was in the bathtub with Carmen, Lucía’s college best friend. There was nothing confusing about it. Nothing that could be misread. They saw me. He froze instantly. She sank lower into the water as if that could hide the truth. Adrián reacted first, whispering with weak desperation, “Nuria… wait… don’t say anything, please.”