Those Damned Preempts!
Dealer starts with an obvious 1C opening with his xxxx-AKx-x-KQ10xx.
Responder, with AKJx-Qxxx-Kx-AJx, has quite a fine collection. Spurning traditional methods, where establishing the GF is a slow and laborious process, Responder is happily playing Golady, such that he can bid an artificial 2C, showing either any GF hand with no 5-card major OR club support and invitational.
Opener is not impressed with his own spades, but the transfer rebid must still be made. 2H.
Responder, on the other hand, likes that a lot. He can set the GF immediately, establish trumps, and keep the two-level still open. 2S.
Opener, of course, next bids 2NT, denying two top trumps. But, Responder knew that already.
Responder can show trumps sufficient to have hope opposite Hxxx or worse and one of the top three club honors. 3C.
Opener does find that interesting. His spades are still quite lousy, but this club development looks quite nice. In any event, the clear next call is 3D. A splinter would be wrong, as he uses Picture Splinters. In this case, that would show a completed club picture, which he has. However, it would also show Hxxx in trumps and would deny a heart control. Wrong on two fronts. 3D works, though.
Responder lacks a heart control, but his spade are two of the top three. He denies the heart control by bypassing 3H, and he shows two top spades by cuebidding 3S.
Back to Opener. His spades are REALLY lousy. But, his overall hand is quite nice, actually. Not quite enough for a serious 3NT, he thinks. 4C works well -- non-serious, with the remaining two top clubs and the implied heart control.
Responder has the serious hand. With a diamond control, he might as well check first as to whether Opener's heart control is first-round. 4D, a showing bid, gives Opener room to clarify.
Opener, in fact, has first-round heart control. Because Opener did not show the serious interest, his 4H call is not Last Train, but rather it is real -- first-round heart control. Of course, Opener could have predicted this auction, which is why he chose to describe rather than ask.
Responder now visualizes a worst-case scenario of xxxx-Axx-x-KQxxx or xxxx-Axx-Axx-KQx. The former seems a tad light on HCP's, so there would likely be an additional major key card somewhere, whether the spade Queen or the heart King.
Opposite the former, then, Responder expects five clubs, four spades, one heart, and a diamond ruff, at a minimum. Strangely, he wants the missing major card to be the heart King, obviously. That makes the hand turn on a spade hook, which seems a fair bet. We might even avoid a diamond loser if the lead is something else. A nice call might be 5H, RKCB in a sense, but Opener looking at the heart suit for the King (and Queen) instead of the spade suit. If Opener hold just the heart Ace, his answer (thankfully playing 1430 here) will be 5S, which can be passed. If Opener has both Ace and King, the "two without" answer of 6C will not be too high. 5H cannot be Exclusion RKCB because Responder previously denied a heart control (and hence cannot be void there).
But, what about opposite the alternative worst-case hand of xxxx-Axx-Axx-KQx? Three clubs, two diamonds, a heart, four spades (if the spade hook works), and a diamond ruff (if spades split 3-3), for only 11 tricks. The 11th trick is clearly in jeopardy, as well, such that the five-level is not all that safe. Plus, if Responder bids that neat 5H call from earlier, the answer will be too high.
Back way up. Opener held a very strong hand at the point when he elected to bypass 3NT and deny serious interest. That election should suggest the flat hand, not the 4315 hand. So, if the auction were to end up at this point, a trusting Responder will have given up.
Opener, with the actual hand, really should show serious interest, despite the cruddy spades. After his 3NT, Responder will cue 4D, showing a diamond control and denying (obviously) any second top club honor. This allows Opener to bid 4H as Last Train, which should now induce Responder to safely make that nice 5H call discussed earlier.
Beautiful teamwork in the bidding, eh?
Damn shame. Could not happen. Opener's LHO held seven diamonds to the AQJ and ruined the potential fun. Nasty Preempts!