to want to catch someone in order to hurt them or punish them.
He'd cheated them and now they were after his blood.
(redirected from be after blood)
be after (one's) blood
To seek revenge on another person. He hit my car, so I'm after his blood now.
be after/out for somebody’s ˈblood
(informal, often humorous) want to hurt or harm somebody, especially as revenge: They have been after my blood ever since I accidentally damaged their car.