Three sessions: a strong advance, a small indecisive day at the top, then a heavy fall. The middle candle marks where the buying stalled.
The first candle is a wide up day. The second has a small body, ideally gapping above it, colour irrelevant. The third is a strong down day closing well into the first candle's body — the deeper it closes, the stronger the signal.
The middle session is the substance of the pattern. After a strong advance, a day where price cannot extend is the first sign that demand has been met by supply.
It is the mirror of the morning star and generally the more reliable of the two, since tops tend to form over several sessions while bottoms can be sharp.
It fails when the third day's fall is a market-wide move rather than something specific to the stock. On heavy index down days evening stars print everywhere and mean nothing individually.
A third candle that closes only marginally into the first body is a much weaker formation than the textbook version, though it is often reported as the same pattern.
Around results season, a small-bodied second day frequently reflects nothing more than traders waiting for an announcement, rather than genuine indecision about value.