Hello, Antonia! Could you provide some context, please? It originally refers to the heart, when you have a sudden emotion (fear, surprise etc...), it skips a beat, it stops beating for a second.
The sisier of the victim is interrogating a suspect. She is also a detective. He is trying to provoke her. Another woman is missing, the suspect's ex girlfriend. He says to her that his girlfriend had tried to kill herself. The detective doesn't wan't to reveal her reaction to that or her true emotions because she is trying to trick him into saying sth that might be a lead
All the explanations so far have been correct for "skip a beat". However, I think that in this particular context, it is a reference to music.[8] The detective carried on without pause; she showed no hesitation or surprise.
(Had she shown surprise, she could not have bluffed effectively)
The negative form "Didn't skip a beat" is a musical metaphor. When a music piece is performed without skipping any beat, it is continuous and fluid. The phrase "didn't skip a beat" means "didn't stop", "relentless", "without pausing", "unhesitating", "unrelenting" etc.
The positive form "Skip a beat", however, has to do more with the heart. The phrase "my heart skips a beat" means "I