2nd bid after a Sputnik and 1NT

The responder's 2nd bid after an overcall in a major, a Sputnik and 1NT rebid by the opener.
Analyze the hand of the 1♦ opener that rebid 1NT after a 1♠ overcall : He has a regular 1st zone hand (12-14HCP), with :

4 or 5 cards in ♦ (opening of his best minor)
Not 4 cards in ♥, otherwise, he would have shown support after his partner's Sputnik
Not necessarily a stopper in the overcalled suit (1NT could have been the only possible bid with 2 or 3 small cards in ♠....).

Now, all you have to do is draw the logical conclusions...depending on your hand !

S	W	N	E

Problème E9998
The opener's rebid at 1NT does not guarantee a stopper in the overcalled suit. It may well be the only possible rebid.

With a hand of 10HCP or less : there is no hope for game

Without support or a 5 cards suit : PASS. Even if the opps start by cashing in 5 tricks in the overcalled suit, you can still get 7 tricks !
With a 5 cards suit, bid it : The contract will probably be easier to play than 1NT especially if you don't have a stopper in the overcalled suit.
Without a stopper in the overcalled suit and 4 cards in the opener's suit : show support.
After your Sputnik double, bidding a new suit at level 2 promises at least 5 cards and less than 11HCP (otherwise you would have bid it in the first round) : It is a stop.