one wrong move and ...; if you make one mistake ...
Fixed expression used to warn that a single misstep could lead to a serious or dangerous outcome. Often followed by a negative consequence.
One wrong move and it could have been a major accident.
If we make one mistake, this operation will fail.
Synonymous conditional form using ば; interchangeable in most contexts.
From 一歩 (one step) + 間違う (to make a mistake) + conditional と. Literally 'if one mistakes one step'.