Allie Beckstrom is a Hound, someone who can trace magic back to its caster. Magic in Monk's world always comes with a price. For most people it's pain proportional to the magic being worked. There are disbursement spells that will allow a caster to decide how the pain will manifest itself (low grade for weeks or a migraine for two days, for example) and ways to cause other people to take the hit. There are (relatively new) laws in place to protect innocent people from having a caster's price Offloaded onto them. There's a suggestion that there's a system set up to allow Offloading onto prisoners.
Unfortunately, for some unknown reason, Allie sometimes pays a double price. Not only does she experience pain, but occasionally she suffers memory loss, too. The memory loss might be her short term memory or it might be a memory from any point in her life.
Allie is hired by a semi-regular client to find out who hit Mamma's 5 year old Boy (she has many adopted sons, all named Boy) with an illegal Offload so powerful that it's killing him. When Allie tries to trace the Offload back to its source she realizes that the magical signature is that of her father.
She hasn't seen her father in nearly 11 years. Her father is a very rich and powerful man, who had decided exactly how Allie should live her life. Instead, she cut off all contact and became a Hound, living paycheck to paycheck.
She goes to confront her father who claims he is innocent. He offers to allow her to work a truth spell involving blood magic, which declares him innocent. Although it's supposed to be impossible to manipulate a blood truth spell, she's convinced her father is lying. In the course of the visit she also learns that Zayvion, a man who is a passing acquaintance who helped her with Boy, was actually hired by her father to follow her. Understandably angry with them both, she quickly removes herself from their presence.
The next day she scans the headlines in a newspaper and learns that her father has been killed. Shortly thereafter she's accused of his murder.
The rest of the book is spent trying to stay ahead of the law and clear her name.
I think the most interesting aspect of the world Monk has created is that society is still trying to come to terms with what it means to have magic in the world. Initially everything was going to be powered by magic (there's a grid under the city that extends everywhere but the slums that distributes magic, but there's also a suggestion it might well naturally in some places) until people learned what the true cost of using magic would be. Now most people used magic in at least a limited way, although there are those who literally live off the grid in no magic zones. The law is still trying to catch up and people are still trying to figure out what magic can and cannot be used for. I find that might more interesting than worlds where magic has always been around but users have just recently come into the open about it and now laws have to be created to restrict a class of people.