baffle
drug-related
first-degree
insoluble
invisible-box
motiveless
real-life
unanswered
unclassified
undescribed
undetected
undiscovered
unexplained
unfathomed
unguessed
unimagined
unnoted
unreckoned
unrelated
unresolved
unrevealed
unsolvable
absolved
devolved
dissolved
evolved
involved
resolved
revolved
solved