In the action card "Silence of Space" you can move through a system containing enemy ships.

What happens if the card is sabotaged? (Either by an Agent or a Sabotage Action Card)

Do you stop in the system containing the enemy ships?

Does the system you activated still hold have your command counter?

Doomslayer

This may not be the 100% correct answer, but it is the way we've played it...

The sabotage card completely undoes the action card against which it was played. Also, as a matter of being nice to everyone else at the table, the sabotage card is played before the action card (against which it is played) begins being resolved, not part way through.

I hope someone else can comment with a definitive answer.

Kerrin2 said:

I can't think of any other reasonable interpretation.  I believe Sabotage states "play in response to the play of an action card," so would have to played right away, thus undoing the action card in its entirety.  If there was a "partial completion" to an associated action card, I think it would cause WAY too many problems in the game. 

The bad news here is that "Silence of Space" probably states "play after activating an area", which means that the player that intended to sneak through an opponent's system is going to lose a CC!  That's punishment enough. 

The Archon is correct here. Since you must activate a target system before being allowed to play "in the silence of space", the Command Counter used to activate the system is lost if "silence" is sabotaged.

 And to answer another part of your question, no the moving units do not stop in the hex with enemy units. You may only (barring SC secondaries and such) ever move units into the system you recently activated. And since the sabotaged AC no longer give your units the ability to sneak by the enemy they may not move at all unless you can find an alternate path (via use of the "flank speed" AC for example).

Also, my personal feelings are that whenever you play an AC, you wait a few seconds to allow other players to react to it. If they do not do so immediatley but want to sabotage it after you've started to move your units, then tough luck for them. They had a chance and didn't take it. The moment has passed and all they've accomplished is to let everyone know they have a sabotage card for later use.