During an opponent turn, after their upkeep, cast Reset for ({U} magic symbol) ({U} magic symbol) .
In response, cast Dualcaster Mage at instant speed for ({1} magic symbol) ({R} magic symbol) ({R} magic symbol) .
Resolve Dualcaster Mage, and target Reset with his triggered ETB ability to copy Reset.
Resolve the Reset copy untapping your lands including Riptide Laboratory.
In response to the original Reset still on the stack, activate Riptide Laboratory's activated ability for ({1} magic symbol) ({U} magic symbol) and tap targeting Dualcaster Mage.
Resolve Riptide Laboratory's activated ability returning Dualcaster Mage to your hand.