A Bitter Feast by S.J. Rozan

Four restaurant workers have gone missing in Chinatown, and the local cops don't seem all that concerned. Peter Lee, a childhood friend of Lydia Chin and a lawyer working on behalf of the Chinese Restaurant Workers' Union, asks her to find them. When a bomb explodes at the union's headquarters, Peter is critically injured and another, unknown man is dead.

Lydia, joined by her partner Bill Smith, goes undercover as a dim sum lady at a local restaurant to find out more about the missing men. She discovers the smuggling of illegal immigrants, heroin, Chinese mobsters, and federal agents working at cross purposes.

Anyone who enjoys mysteries that emphasize characters, such as the books of Julia Spencer-Fleming and Elizabeth George, will want to read this series.