Black Lagoon: Roberta’s Blood Trail (2010–2011), directed by Sunao Katabuchi and based on the manga by Rei Hiroe, follows the Lagoon Company as they become involved in a violent revenge mission led by Roberta. The story focuses on escalating conflict between criminal groups and the psychological consequences of violence.

Från IMDB:
The 'bloodhound' awakens when her master, and head of the Lovelace family is assassinated.