गूफ़

While Miss Marple is chatting with the gardener and using the sprayer to kill the bugs, she generously sprays the top of the wall where the gardener's coffee cup is resting. A few moments later he drinks from it, but apparently suffers no ill effects.

The "posh car" owned by the tour bus company owner is a bright yellow roadster that looks suspiciously like a 1957 Ford Thunderbird, though it may have been a British make of similar design. But the headlights and taillights are unmistakably from the period of 1955-1957. If this mystery series is set in the post-WWII era of 1946-48, that car would have been about 10 years before its time.

In Part 2, Gwenda mentions that her step-mother Helen went missing "about 20 years ago" & "shortly before the War" (i.e. mid- to late 1930s), which means that this story is, in fact, set in the 1950s (as are most of the Joan Hickson Miss Marple adaptations). Thus, the yellow car may not be an anachronism at all.

All the telephones ring in the U.S. (long ring) style rather than the double short ring used in the UK. In one scene a phone continues to ring after the character Giles Reed has brought the receiver to his ear.