Ghostly Flicker is cast targeting the 2 Walls.
It resolves, the Walls enter and trigger. They do not go onto the stack.
Ghostly Flicker goes to the graveyard as the last part of resolving.
Now, before players get priority, the games checks to see if any triggers are waiting to go onto the stack.
There are, so they do.
When they are put onto the stack, the targets are chosen.
Both Bolt and Flicker are in the graveyard at this point, so they are legal targets.
The triggers resolve and both end up back in your hand.
You cast Bolt and Flicker again and continue.
For example, let's say I have two Mnemonic Walls on the battlefield and a Lightning Bolt in my graveyard when I cast Ghostly Flicker.
(Obviously wanting to target the Mnemonic Walls with my Ghostly Flicker and return the Lightning Bolt and Ghostly Flicker to my hand.)
Thanks!
It resolves, the Walls enter and trigger. They do not go onto the stack.
Ghostly Flicker goes to the graveyard as the last part of resolving.
Now, before players get priority, the games checks to see if any triggers are waiting to go onto the stack.
There are, so they do.
When they are put onto the stack, the targets are chosen.
Both Bolt and Flicker are in the graveyard at this point, so they are legal targets.
The triggers resolve and both end up back in your hand.
You cast Bolt and Flicker again and continue.