UncommonWhere does a Flow spell countered by Abandon go?
If no other replacement effects apply, it is banished rather than returned to its owner's hand.
Abandon's "Counter a spell" instruction targets a finalized spell on the chain.355.10355.9.a.2 Countering would clear that spell from the chain and put it in the trash.426.1.a426.1.a.1 Abandon's later instruction replaces putting it in the trash with returning it to its owner's hand.158.2369.1 Because Abandon's counter, rather than the spell's own execution, makes it leave the chain, the delayed replacement effect created by [Flow] also applies and would banish it instead.829.1.b.1
Both replacement effects apply to the same departure event, so the spell's controller chooses their order.372
The result is the same in either order. If [Flow] applies first, the spell is banished instead of going to the trash, so Abandon no longer has a qualifying event to replace.370.1 If Abandon applies first, it replaces the original event with the spell leaving the chain for its owner's hand.370.1.b That replacement event still makes the spell leave the chain, so [Flow] applies and banishes it instead.370.2 An additional replacement effect joins this ordering and can change the final destination.370.2372