Ann Walsh was a former servant at the Sun Hall and a member of the Scarlet Guard. She died a notable death, saying "For Tristan."
Walsh first encounters Mare when she appears at the Barrow house to take Mare to work as a servant at the Hall. Mare notes that she is surprised by Walsh's kindness towards her. Walsh helps Mare adjust to being a servant, giving her the advice "Say nothing. Hear nothing. Speak to no one, for they will not speak to you." Cal later explains that he choose Walsh to get Mare because she was from the Stilts, just as Mare.
Before her death, Walsh was seen helping the Scarlet Guard multiple times. She gave Mare the message in her water revealing when to meet Farley.
Walsh was captured by Silver soldiers, including Ptolemus and Cal, while keeping watch in old tunnels by orders of the Scarlet Guard. Mare explains that Walsh was watching the train tunnels, making sure the way was clear for her and Maven to get back from Naercey. Before Elara makes her sing, Walsh swallows a suicide pill and says the words "For Tristan" then dies within seconds.
Mare describes Walsh as a playful and smiling young woman.