Stephanie Plum was a lingerie purchaser but when she lost her job, she was desperate. There were bills to pay and she couldn't seem to find a job that was suitable. So, she went to see her cousin Vinnie who was running a bond enforcement agency and blackmailed him in order to get work. He agreed to pay her a percentage of the bail money he had paid for individuals who had skipped their Court date, if she found them and turned them into the police.
Stephanie is not very good at her job but the commission she makes is enough to finance her sparse lifestyle.
Stephanie is usually just focussing on paying her rent but was surprised and pleased to have an opportunity to visit Hawaii. She hoped that she would have a nice, relaxing holiday. It ended up, however, that her two love interests came to Hawaii and had a horrible fight with each other.
Joe Morelli is a Trenton, New Jersey police officer who Stephanie has been attracted to since her childhood. The problem with their relationship is that they sometimes want to commit to each other - but never at the same time so over the years, it has been "on-again and off-again".
Ranger, a security expert, who has been Stephanie's career mentor, is also extremely attractive to Stephanie. He, however, has an air of mystery about him and just doesn't seem to be interested in more than a few romantic encounters. He's just not the type that she would expect to commit to her - or anyone.
After the fight, Stephanie took both of her lovers to a Hawaiian hospital and then headed back home without them.
Matters got worse after the man seated next to her on the plane disappeared during a layover. Then the FBI and a motley group of thugs began chasing Stephanie in hopes of recovering a photograph that they believed the man on the plane had been carrying.
While Stephanie is being hounded for the photo, she still has to make a living by finding individuals who skipped their Court date after her cousin Vinnie posted bail for them. His office, however, was recently destroyed and even the temporary headquarters went up in smoke, so his staff have to be flexible.
Stephanie's Grandma Mazur, the teen-aged thinking senior, thinks that Stephanie needs some help in securing a man, so she has a friend make up a love potion. Lulu, the former prostitute who sometimes helps Stephanie with her work, drinks it instead of Stephanie and immediately falls in love with the man who they have been trying to turn in to the authorities.
Even Joyce Barnhardt, an enemy of Stephanie's causes problems. She is in hiding and decides that she should be staying in Stephanie's apartment.
So, Stephanie is facing problems in her career and in personal life. She doesn't even have the ability to go home in order to get away from problems because Joyce is there. Joe and Ranger are awkward around her because of the incident in Hawaii and neither of them want to talk about it to find any resolution.
It's just one problem after another in "Explosive Eighteen" but Janet Evanovich is able to add enough humour and creativity that the reader is captivated.