Playing fairly standard 5 card major.
Pard opens 1H in second seat, and after your 1NT response, West(who had previously dealt and passd !!!) bids 2S.
You assume your pard's double shows extras, but not a specific shape: probably in the 17-20 range, likely balanced or some 1-5-(43).
You can trust partner, he is a good player, but any inferences from opps bidding will be useless, they are certainly less than advanced/intermediate.
What do you bid ?

Help

(p)-1♥-(p)-1NT
(2♠)-DBL-(p)-?