The HA is led against the unambitious contract, but let us assume you are in SEVEN. plan play before reading on.
Let East try to keep parity with dummy in Hearts. You run N minus 2 trump to this end-position.
Now cross to SA,cash SK to turn the screw on E in the hexagonal position
What is E to keep on this trick? If he throws a H equal, advance HQ ruff out, return via CA to enjoy H8. If he throws a club, Cash CA ruff a heart and enjoy C7.