Looking for an old story
I'm trying to find a story.
In it, a secret agent is sent into an enemy facility. There, he is captured and administered the latest in truth serums, which has unfortunate consequences for short term memory.
SPOILERS
So the truth serum messes with the transcription of short term memory, meaning that every so often, he snaps back to before the mission. The story at that point has the imperative "Look Around".
At one point, the reset happens when he is half out of a ventilation duct, and he has to figure out if he was going in or coming out. He was sent to assassinate a scientsit, but instead snatches him. He has an implanted capsule of an irritating chemical, which he presses on to break when his mission is finished, as they anticipated his memory issues.
The only other details I remember are a hypersonic jet, a spherical escape module, and the likelihood that the story dates from the 1960s or maybe even 1950s.