The Alert keyword says the attack occurs whether or not the targeted enemy is engaged with the evading investigator or not. However evasion states that an Evade action can only be performed against an enemy engaged with you. Are there cases where you could attempt to evade a non-engaged enemy?

You can also (theoretically) using cards. The evade action would require you to be engaged, but there could be cards you can play that evade additional enemies at your location regardless of engagement. I'm not sure that any of these can fail, but that's what I would assume would need to occur.

Check out the text on Fire extinguisher. I imagine if you tried to use the fire extinguisher and failed, you would take damage from each enemy at your location with alert engaged enemy at your location.

https://arkhamdb.com/card/02114

EDIT: I actually think Fire Extinguisher may be the ONLY card like this at the moment that I can think of.

EDIT 2: Actually Fire Extinguisher says each enemy engaged with you... sooo nevermind. Okay, I can't think of a case actually.

@Soakman You would only be attacked by the specific enemy you made the test against.

There are Cunning Distraction and Stray Cat, but they're both auto-succeeds.

I can only imagine that there will be a card introduced, perhaps a rogue card, that will let you attempt to evade an unengaged enemy in order to exhaust it. It might just be future-proofing?

11 minutes ago, Soakman said:

I can only imagine that there will be a card introduced, perhaps a rogue card, that will let you attempt to evade an unengaged enemy in order to exhaust it. It might just be future-proofing?

Probably. Or evade something that's engaged with someone else.

There could be enemy- or location-specific abilities as well. Unspeakable Oath has one that lets you evade certain enemies at the location, but it again is an auto-succeed. Peter Clover -- again, auto.

Just now, Soakman said:

I can only imagine  that there will be a card  introduced  , perhaps a rogue card, that will let you attempt to evade an unengaged enemy in order to exhaust it. It might just be future  -proofing?     

That would be a good level 1 or 2 card especially in multiplayer.

It could go the other way too, with enemies that allow anyone at the location to evade them.

18 minutes ago, Buhallin said:

It could go the other way too, with enemies that allow anyone at the location to evade them.

Lol, like the opposite of massive almost. I can't imagine a need to do this, but you're right in that it definitely could go that way.

1 minute ago, Soakman said:

Lol, like the opposite of massive almost. I can't imagine a need to do this, but you're right in that it definitely could go that way.

I'd see it as a potential limiter on otherwise very nasty enemies, like the Unspeakable Oath's...

I really need to figure out how to do spoiler tags here.

1 minute ago, Buhallin said:

I'd see it as a potential limiter on otherwise very nasty enemies, like the Unspeakable Oath's...

I really need to figure out how to do spoiler tags here.

brackets 'spoiler' and brackets '/spoiler'

I always forget though, haha.

3 minutes ago, Soakman said:

brackets 'spoiler' and brackets '/spoiler'

I always forget though, haha.

I actually tried that and checked the preview, it doesn't show up right there.