Following a string of art heists, Prudence asks Nancy Drew to stay at her beloved Ca' while the sleuth helps the Italian GDiF to solve the crimes. During her stay, Nancy roommates with Helena Berg, an Austrian journalist who is also Margherita's guest. A young British art-restorer called Colin Baxter can also be found at the Ca', having been hired by Margherita to renovate the place.
The Ca' has a small walled courtyard/entryway where the residents can collect deliveries. Visitors and residents must walk up a flight of stairs to reach the front door, which opens to the main hall. The right half of the main hall has tarps and scaffolding on the walls and wooden planks on the floor during its renovation, as well as a worktable Colin uses to restore mosaics. He keeps a microscope, books on art, a valuable golden Etruscan figurine, and later a Chinese puzzle box on the table's surface.
On the left half of the Ca' is a low table and a couple chairs for lounging. Nancy can find and sample a half-eaten box of chocolates on this table. Across from this area is a small desk where Helena does her writing. Between desk and table is a stairway leading to the roof, and behind Helena is the door leading to her and Nancy's room.
Margherita spends almost all her time sunbathing in a white deck chair on the Ca's rooftop. Next to her are two chairs around a small table. When Margherita is away, Nancy can see that there are a couple water glasses and a letter Margherita has written. There are many plants growing on the roof of the Ca', including strange flowers Prudence obtained through the Hilihili research center in Hawaii. Margherita allows Nancy to cut and sell them, as she says they grow like weeds, but before she can touch them Nancy must first battle the wasps that guard the blooms. Nancy must also come up to the rooftop to spy on Antonio Fango in the Argon building across from the Ca' for her GDiF assignment. When Margherita questions her, Nancy can choose to tell her that she's birdwatching, admiring the architecture, or truthfully say that she's spying on someone.
Nancy sleeps on the left half of the bedroom while Helena sleeps on the right. Between the beds is a door that opens on to the balcony, from which Nancy can see the canals and hear passing Venetians. There is a telephone on the right of the balcony door from which Nancy can call Prudence Rutherford, her boyfriend Ned, and Joe Hardy. On Helena's side of the room, there are postcards to her friends and family and a framed picture of herself on her dresser and a book on Venice on her table. On Nancy's side of the room, there is a wardrobe that can be used to change Nancy's appearance, as well as provide a space for Nancy to place her toiletry bag and Mr. Woogle Wogle. To the left of Nancy's bed is a door that leads to a bathroom.