Solana Rojas is one of the darkest and most dangerous sociopaths Kinsey Millhone has ever encountered.

Kinsey’s next-door neighbor, Gus, is a 90-year-old crank who can be counted on to call the authorities on code violations or shake his fist at skateboarding kids. He has been conspicuously quiet for the past two days. Then one morning, as Kinsey is leaving for her office as an insurance investigator, she and her landlord Henry hear a wail coming from Gus’s house. They find him crumpled in a corner with a badly dislocated shoulder and cracked ribs from a fall in the shower. Once they call an ambulance and get him to the ER, they discover that his only living relative is a niece who lives in New York. Due to the nature of his injury, he is released to a nursing home, which Gus will have none of. He is fully mentally competent and soon will be able to care for himself, but he needs someone to look in on him on a daily basis for several months.

Neither Henry nor Kinsey is able to give the level of home care needed to keep him in his cozy little house. Kinsey urges the niece to come straighten things out; she is concerned but cannot give up a lucrative career in New York to care for her ailing uncle.

The response to an ad she runs produces only a few unpromising prospects, none of whom seem anxious to care for the crotchety old man. Then Solana Rojas shows up and, unlike the previous applicants, appears highly qualified, puts up with his temper and eagerly takes the job starting immediately. The niece, relieved to have someone take over so she can get back to New York, leaves her uncle in Solana’s hands and hires Kinsey to do a brief background check. Kinsey finds her resume and letters of recommendation in order, even interviewing two prior employers by phone, and gives a positive report.

Solana is an expert at creating false identifications. Her elderly patients are frequently mentally incompetent or died under her care. Their relatives, if they have any, are never suspicious when their elderly loved one passes away, and some patients, grateful for Solana’s apparently tender loving care, have even left something in their wills.

With financial resources from her last scam dwindling, Gus is the perfect target. Solana can assume the identity of a fellow employee who she learns is leaving the state to go back to school. Through a carefully concocted personal identity theft scheme, Solana turns her credentials as a nurse’s aide into those of a registered nurse. She practices using cosmetics, a dye job and a hairstyle change to resemble her co-worker. She lifts her driver's license from the restroom, and the transformation is complete with little risk of discovery. Now her prey is in easy striking distance, and a mentally competent but physically helpless old man with no near relatives to check on him is ripe for the picking.

As silent and lethal as undetectable poison, Solana begins to set the stage for the solitary Gus’s demise. Through lies, deception, deliberately confusing times of day and drugging his food, he soon appears to have dementia and memory loss to friends who visit. His distant niece who trusts Solana enables her to take more responsibility with his day-to-day needs.

Kinsey begins to suspect that something is wrong when Gus’s personality changes and starts to look for evidence of wrongdoing. Solana’s sociopathic behavior and paranoia soon turn on Kinsey, and she finds herself the object of Solana’s abuse.

As current as today’s headlines, Sue Grafton tackles the problems of identity theft and elder abuse in an exciting new novel --- the 20th in her legendary alphabet series.T IS FOR TRESPASS is more than a good mystery; it is an alert to the dangers that await us all if we are not aware of how easy it is for an unscrupulous person to insinuate themselves into a family member’s life.