The event drew 200 guests for cocktails and a "strolling supper" that Post 22 catered.
The library's lobby and adult reading room were decorated with twinkling lights, black-and-red tablecloths, flowers and accessories for Halloween.
A silent auction was part of the evening when local residents played suspects in a funny James Bond-type plot.
The guests teamed up to ask questions and solve a murder.
The event raised money for the New Rochelle Public Library Foundation, a volunteer fundraising and advocacy organization working to ensure the future well-being of the library.
Click here to follow Daily Voice New Rochelle and receive free news updates.