A Charm refers to a blind-play in which someone plays an unrelated card from their Fourth Finesse Position. For example, if a player's hand is completely unclued, their Fourth Finesse Position is slot 4.
Charms fall outside of the Signal Shift framework. Instead, playing from Fourth Finesse Position is required in order to disambiguate the clue from being a Finesse, Ejection, or Discharge.
Just like a Bluff, a Charm can only be performed on the very next player.
The Out-of-Order Finesse always takes precedence over a 4 Charm or a 4's Double Bluff, because of Bob's Truth Principle.
For example, in a 4-player game:
It is the first turn and nothing is played on the stacks.
Donald's hand is as follows, from left to right: red 4, red 1, blue 3, blue 3
Alice clues red to Donald, touching the red 4 on slot 1 and the red 1 on slot 2. This is a Play Clue.
Bob knows that this could be the truth as an Out-of-Order Finesse. If that is the case, he should clue number 4 to Donald, allowing him to play the red 1. Then, Bob can blind-play the red 2 and the red 3 (into the playable red 4).
Bob knows that this could also be a 4 Charm, since the red 4 is three-away-from-playable and Bob does not see any other red cards on Finesse Position.
However, Bob knows that he should always assume the truth over a lie, so he assumes that Alice intends for an Out-of-Order Finesse.
Normally, after an Unknown Trash Discharge, non-focused cards are known to be "good".
However, what if a player performs an Unknown Trash Discharge where all of the non-focused cards are trash? A Discharge would incorrectly signal that the non-focused cards are useful.
Instead, this should signal a Charm on the very next player.
For example, in a 3-player game:
All of the 2's are played on the stacks.
Alice clues red to Cathy, touching a red 1 on slot 1 and a red 2 on slot 2.
Normally, Bob would treat this clue as an Unknown Trash Discharge. However, if he Discharges, then Cathy will discard the red 1 and mark the red 2 as either a red 3, a red 4, or a red 5, which would be a Lie.
Instead, Bob knows that this signals an Unknown Trash Charm, so he blind-plays his Fourth Finesse Position. It is a blue 3 and it successfully plays.
This convention only applies in the Low Score Phase.
If a card could be freely gotten by initiating a 5 Pull, it would be very strange if the 5 Pull was declined and the card was directly touched as a 1-for-1.
When this occurs, this player is trying to communicate something deeper - a Charm on the very next player.
Normally, when a card is blind-played after an innocent-looking Play Clue, the clue receiver knows to not play that card anymore. In this situation, since the Fourth Finesse Position card was played instead of the First, Second, or Third, the clue receiver will know that their card is still playable and that the unclued card directly to its left must be a 5.
This untouched 5 is now globally known; everyone on the team should treat it as a Chop Moved card.
For example, in a 4-player game:
Red 1 is played on the stacks.
It is the Early Game and the Low Score Phase.
Alice clues red to Cathy, touching a new red 2 on slot 2.
Cathy hand is, from newest to oldest: blue 5, red 2, blue 3, blue 2
Bob sees that Alice could have cleanly 5 Pulled Cathy's red 2. (It is globally known that Alice had another Play Clue to give, so a number 5 clue would not have been interpreted as a 5 Stall.)
Bob knows that this signals a blind-play:
A First Finesse Position blind-play would look like a Bluff on a red 3, which would be a Lie.
A Second Finesse Position blind-play would look like a 5 Color Ejection on a red 5, which would be a Lie.
A Third Finesse Position blind-play would look like an Unknown Trash Discharge on a red 1, which would be a Lie.
Thus, Bob knows that this must be a Safety Charm. He blind-plays his Fourth Finesse Position. It is a blue 1 and it successfully plays.
Cathy knows that she must have the red 2. She also knows that her slot 1 card is a 5 that could have been used for a 5 Pull. Cathy marks the 5 as being Chop Moved for later.
4 Charms take precedence over Safety Charms.
More examples of a Safety Charm can be found here.