The idiom "on the case" means to be actively investigating or working on something, usually to solve a problem or find information. It can also refer to someone who is experienced and competent at their job or task.

The idiom "good account of" means to have a detailed explanation or accurate information about something. It can also imply being able to provide an account or report about something, as well as having a thorough understanding of a topic.

The idiom "cut and thrust" refers to a lively, competitive, and sometimes confrontational exchange of ideas or opinions. It can also describe a situation where people are arguing or debating intensely.

The idiom "head-on" refers to facing a situation directly and without hesitation. It means approaching an issue or problem with a clear and determined attitude.

Red Letter Day is an idiom that refers to a day of great significance or importance. The term "red letter" historically referred to a bold, colorful ink used for important documents, such as birth certificates and marriage licenses.