What happens when Hidden Blade is chained with Gust or Flash in different orders?

Ruling: When Hidden Blade's target becomes illegal before it resolves (due to being returned to hand by Gust or moved to base by Flash), Hidden Blade resolves with no effect and no one draws cards. When Hidden Blade resolves first (Chain 2), it kills the unit and the controller draws 2 cards, then the Chain 1 spell (Gust or Flash) resolves with no effect since its target is gone.

Sequence:

• Hidden Blade Chain 1, Gust Chain 2: Gust resolves first returning unit to hand, then Hidden Blade resolves with no effect (no draw)
• Hidden Blade Chain 1, Flash Chain 2: Flash resolves first moving unit to base, then Hidden Blade resolves with no effect (no draw)
• Gust Chain 1, Hidden Blade Chain 2: Hidden Blade resolves first killing unit and controller draws 2, then Gust resolves with no effect
• Flash Chain 1, Hidden Blade Chain 2: Hidden Blade resolves first killing unit and controller draws 2, then Flash resolves with no effect

Nuances:

• When a spell resolves without a legal target, resources are still spent and the spell is discarded
• A unit must be a legal target when the spell is cast, but may become illegal before resolution
• Cards do as much as they can even if some parts aren't possible (e.g., Flash targeting two units would still move the other unit)