- "Too many crooks always ruin the neighborhood."
- — Tagline, from the front cover
Thick as Thieves is the 29th book in The Hardy Boys Casefiles series.
During a daring robbery of rare gems, Frank and Joe spot the thief. Their old enemy Charity has turned up in Bayport -- and once again she manages to slip through their fingers. The Hardys track her to San Diego, where they run smack into a crook's convention.
A group of master criminals are planning the crime of the century -- and they think Joe is one of the dishonored guests. Joe joins the gang, but then he disappears in a bomb blast. Frank is left to avenge his brother's death against all odds -- as he tackles a killer tag team with a secret weapon...and a lethal lady named Charity.