I assume it has something to do with countering her poison? 

Or do we take all the letters added and removed from the Riddler's original words....


All together:  NPLSTHPIKIOUOLML

Plant:
NPLSTHP

Animal:
IKIOUOLML

Last edited by OnlyInThisLight (08-18-2012 11:28:47 PM)

The con man should die, get a serious case of hay fever, or (to quote Riddler) wither away.

...so we lose a letter.Conman.... Conan?

** SPOILERS **
This post will reveal the entire worked solution to this riddle.  If you're still working on it, stop reading here!

The diagram leads you to expect something in the vein of a crossword puzzle, and indeed the clues are in a straightforward crossword style.  The clues vary in difficulty, but most of them have fairly unambiguous solutions.  For instance, clue 5, “not poetry,” should clearly be PROSE.  The problem is that PROSE does not fit into blank 5, which only has room for four letters.  In fact, none of the clue solutions fits into the corresponding blank.

Happily, the Riddler has given us some idea what's going on.  Poison Ivy has played with the clues.  Her touch “may make plants grow, but it makes human beings and animals wither away.”  We are supposed to “counter the effects of her toxin.”

It may be helpful at this stage to solve as many clues as we confidently can.  This will help us understand what we're supposed to do with the answer words, and what the Riddler's cryptic hint means.  We may notice a pattern: every answer word is either one letter too long for its blank, or else one letter too short.

At this point, we might have an “aha!” moment.  If every answer word is either one letter too long or one letter too short, perhaps we have to make some of the words shrink and others grow to fit their blanks.  How do we do this?  Well, let's consider some of the words that we feel sure will need to shrink.

PROSE (clue 5)
BLUSH (clue 6)
IRISH (clue 10)
GRASPS (clue 15)

If we try to shrink these words by removing letters from them, we soon discover that each of them can lose a letter to leave the name of a plant: ROSE, BUSH, IRIS, GRASS.  These plant names fit the blanks.  Ivy's toxin made the plants in the clues grow (into PROSE, BLUSH, etc.); by reversing the effects of the toxin, we shrank them again, and now we can enter them in their blanks.

What about the words we think will need to grow?  Here are a few we feel pretty sure we've solved correctly:

MONEY (clue 3)
WATER (clue 4)
SCOT (clue 11)
ION (clue 16)

By now we have some idea what to expect: not plants this time, but “human beings and animals.”  Indeed, if we try to grow these words by inserting letters into them, we can pretty easily find MONKEY, WAITER, SCOUT, and LION.  These fit into the blanks.  Again, Ivy's toxin has worked as advertised: it made the human beings and animals wither by deleting a letter, and we have reversed the toxin by growing them back to normal.

Now that we know what's going on, we can take a crack at the harder clues; we'll know we've gotten it right when we can transform the answer into a plant by shrinking it, or into a human being or animal by growing it.  In order, the clue answers are SOLDER, VIOLENT, MONEY, WATER, PROSE, BLUSH, CORNER, SHEATHER, TWEED, IRISH, SCOT, FLAMING, STARING, SALON, GRASPS, ION.  They are transformed respectively into SOLDIER, VIOLET, MONKEY, WAITER, ROSE, BUSH, CORONER, HEATHER, WEED, IRIS, SCOUT, FLAMINGO, STARLING, SALMON, GRASS, LION.

In the diagram, one of the rows of blanks runs from left to right in an uninterrupted line.  When the final answers – that is, the plant, animal, and human names – are entered into their blanks, this row reads IVYTOUCHESCONMAN: “Ivy touches con man.”  A con man is a human being, so when Ivy touches a con man, he should shrink.  Taking a letter from CON MAN leaves CONAN, the riddle solution.