adverb (or adjective)
or upon the spot
1. : before moving or without further consideration : at once : immediately
decided on the spot
2. : at the place where action is required
sent to investigate on the spot
found everything he needed right on the spot
3.
a. : in a position of being held responsible or accountable or of being required to furnish a satisfactory explanation or reply : in trouble or difficulty : in a spot
b. : in a position of danger especially of murder or assassination (as by way of reprisal) — often used in the phrase put on the spot