1. Three notrump. Before discussing the proper action, it might be best to define the meaning of a non-jump overcall on the two-level. Generally, this shows not only a very good suit but also the values for an opening bid.

Once this definition is accepted, it becomes clear that this is a game-going hand, and the most likely game is in notrump. Two notrump, which would be invitational and not forcing, would be totally inadequate.

2. Three diamonds. A partner who overcalls is usually much more interested in learning if you have support for his suit and the values for a forward-going bid than to learn whether you have a suit of your own and a hand of indeterminate strength. It is therefore better to raise diamonds with the given hand than to bid two hearts, which you could also do with

You are hoping, after you raise diamonds, that partner will be able to bid three notrump.

3. Four diamonds. Here you want to invite game in a suit rather than notrump. True, you have only 10 high-card points, but your distributional features more than make up for your lack of high-card strength. Another way of implying strong interest in game in diamonds would be to cuebid two spades, a method currently popular with many players.

4. Pass. Chances for game are poor, considering your lack of support for partner’s suit. To bid two hearts with a four-card suit is out of the question, and two notrump is likewise not feasible because partner’s diamonds might prove useless as a significant source of tricks in notrump. Despite your singleton diamond, partner is a favorite to make two diamonds, so you should get out of the bidding while you still have a chance for a plus score.

5. Four hearts. Given partner’s two-level overcall, you should be a heavy favorite to make four hearts, and you should bid it directly. It would be wrong to bid only three hearts, which is highly invitational but not forcing.

Tomorrow: It’s almost magic.