Gay is one of Joan Watson's "Irregulars" who she employs when she needs expertise in geology. She is the first Irregular that Watson recruits. Sherlock Holmes has also used Gay's expertise. Gay is a geology fellow at NYU and is a lesbian.
|While looking into a murder cold case, Watson discovers an unusual rock in the photo. Gay indicates that the rock was dug up from deep in the earth which results in Watson and Gay going to Riverdale where they find rock is still in the yard of the murder victim. Watson takes the rock which makes Gay uncomfortable so she leaves. Watson has a CT scan performed on the rock which reveals a complete nanotyrannus skeleton inside. Later, she's asleep on the couch in The Brownstone library at 4:00am while Holmes blasts music to stay awake. Holmes tells Watson that he's used Gay to deduce why the nanotyrannus was destroyed. ("Dead Clade Walking")
|Holmes uses Gay to test the water in the Hudson River while investigating a murder they believe a construction company was involved in. They discover the company siphoned sand from the river. Later at the 11th Precinct, Gay accompanies Watson and Holmes as they explain the impacts this will have to Detective Bell and Captain Gregson. Gay uses a computer model to show that the siphoned sand will not only cause heavy metals to leech into the river but also cause erosion of the support pylon of a bridge which will cause it to collapse. ("Sand Trap")