2D = multi (weak two in a major or various strong types). Partner overcalls 2NT showing 16-18 with both majors stopped. How do you plan to advance? Options are 3C puppet stayman, 3D/H transfers, 3S minor suit stayman, 4C gerber (sorry).
If you pick puppet stayman, it goes like this:
What next? Pass is forcing, if you pick this partner will double.
ahydra