SOMEWHERE in this puzzle there are 11 double-crossers; that is to say, there are 11 letter pairs each shared by a single Across answer and a single Down answer. One letter of each such pair belongs in the square where the two words intersect, but the other letter should be shifted horizontally to a square in the unclued and otherwise uncrossed entry at 4 Down. Solvers will need to determine which letter of the double-crossing pair is to be shifted. When all the shifting double-crossers are in place, they will form an appropriate phrase. To protect the identities of the double-crossers, lengths are not given. Six answers are capitalized.
1. Place double-crossers the wrong way in beginning
7. Cure for disrupting nocturnal twitch
11. Absorbing composer scores Don Juan and the like
12. Enlightened, made like Sullivan?
13. Some bread bearing excellent image of Mary
15. Try saving the last snow leopards and whales
16. Islander's expression of surprise captured by Italian painter
18. Stunners married hotshots
20. Ending in movie is phony
21. Faithful arrive, mostly wearing gloves?
23. Finally, tell a long story about northern Italian food
26. Fashion poem starting with meter
27. Cracking up at a rusty bunch of carvings
28. Comrade in Italy's capital taking in Dante's earliest, peculiar sort of writing
29. Hamlet characters' dispatch from the east about Ophelia's end
30. Viking running back calls one of the Reagans
1. In part of the fall, briefly, lake lay still
2. Heartless, dirty rotten police
3. Given new supplies after changing diet, fret
5. Journey to remote eastern kingdom, initially
6. Constrict view behind the front
7. Some politicians organized Persian club
8. Predictions about splitting timberlands
9. Double-check street in bad shape
10. School in southern city with average rank
14. Singer's rustic pitch, in C
15. Uranium carried by mine conveyor, along with a bombshell
17. Indulgence for chestnut striking the head
18. Writer of French article in Mother Earth
19. Interrupting Dershowitz, cut short sore loser (hyphenated)
21. Crook from one N.E. state held in another (two words)
22. Produce-craving elder
24. Prison riot?
25. Pervasive atmosphere near Omaha's center
The Atlantic Monthly; September 1997; The Puzzler; Volume 280, No. 3; page 119.