A Second Hand Cat by Steve Lohengrin
In a gray world, can anything be just black and white?

Officer Charles Wall was hailed as a hero, but a traumatic brain injury left him dealing with constantly shifting and extreme emotions. After a violent fit of rage, his police friends helped him avoid prison, but he had to give up his pension and endure nearly two years in a psychiatric facility, crushed by guilt and barely able to speak.

After his release, he moves into a City Housing apartment, using the name Roland Wall to avoid attention. No longer financially comfortable, he works part time at the Library for food money, and the sort of people he once thought were beneath him look down upon him. Isolated and frustrated, he constantly struggles to control his anger, because he can't afford to fail.

Then one of his very few friends is brutally murdered, and he inherits Claude, her 'nice, quiet old man' of a cat. But Claude turns out to be a homicidal mess who needs expensive medicine every day, and just wants to be left alone. They have much in common.

When another woman is murdered, it's discovered that Wall had a connection to her as well. The City Police dismiss him as a suspect, but since he doesn't remember where he was when it happened, he can't rule himself out.

Because both victims were lesbians, ambitious FBI Special Agent Netty involves himself in the case, hoping the lurid headlines will give his career a boost. After evidence that could have been used against Wall disappears, Agent Netty, who knows about Wall's past, locks his sights on him.

Meanwhile, Wall finds out that one of his neighbors is spying on him, the others fear him, the local newspaper is vilifying him, a mysterious woman is stalking him, even his own psychiatrist is angry with him, and it's always raining. It's all starting to make him feel the way he did when he committed murder before.

And the cat is not helping.

Or is he?