Be quick (or slow) off the mark be fast (or slow) in responding to a situation or understanding something.
the mark of the beast in Revelation 16:2, a sign placed on followers or worshippers of Antichrist. In extended use, the phrase was first used to mean an indicator or symptom of heresy, and then more generally a sign of infamy.
wide of the mark a long way away from the intended target, inaccurate.
See also mark of Cain, mark with a white stone, X marks the spot, mark of Zorro.