swallow hook, line, and sinker
swallow (something) hook, line, and sinker
To believe completely and unquestioningly that something is true, especially that which is deceitful, misleading, or untrue. I told them that I like this stupid school, and they swallowed it hook, line, and sinker—I guess I'm a pretty good actress. I can't believe they swallowed his stupid story hook, line, and sinker.
swallow something hook, line, and sinker
Fig. to believe something completely. (These terms refer to fishing and fooling a fish into being caught.) I made up a story about why I was so late. The boss swallowed it hook, line, and sinker. I feel like a fool. I swallowed her lies hook, line, and sinker.