This one appears fairly laborious at first look. I will take it at face worth that the Montagues themselves are telling the reality, and due to this fact that there’s just one thief / potential liar, and likewise that the portray just isn’t on the backyard or the pond.
You would possibly begin by searching for two or extra statements that create some form of contradiction, which might point out that one among them have to be a lie. For instance,
Taylor says that if the portray is on the windmill, then Jessica is responsible. But when the portray is on the windmill, then that makes Beth’s assertion a lie, which might suggest there are two responsible events, which contradicts our assumption that there’s just one. So we’d deduce that the portray is NOT on the windmill (or that Taylor is the liar). And proceed from there.
One other method is likely to be to imagine the portray is at a sure location, after which work out which assertion(s) can be lies for those who have been proper. For instance,
You would possibly begin by assuming that the portray is on the boathouse. However then that will imply each David and Karen are mendacity, which once more contradicts our assumption that there is just one liar. So we’d conclude that the portray is NOT on the boathouse. And so forth.
I feel I’ve discovered an answer which is solely in line with the entire situations of the puzzle, though I need to admit it’s kind of unsatisfying and it actually doesn’t preclude the existence of different options:
It appears potential that the portray is on the cottage, and the thief is Grant. The entire company, in addition to the remainder of the workers, can be telling the reality. Beth the banker begins on the windmill; Charles the gerontologist begins on the cottage; David the entrepreneur begins on the pond; Frank the filmmaker begins on the mansion; Jessica the composer begins on the boathouse; Karen the decorator begins on the lighthouse; and Taylor the legal professional begins on the backyard. I suppose this would possibly suggest that Charles discovered the stolen portray on the cottage however did not say something? There’s so much about this puzzle that is ambiguous so I am undecided if that is an unreasonable assumption.
Per the remark from @WoomyRogue, I am assuming that neither the Montagues nor the workers can lie. This makes the puzzle considerably simpler, and I consider I’ve discovered the answer. First,
The portray can’t be on the backyard or the pond (Alistair). If the portray is on the windmill, then Beth is mendacity. This additionally means both Taylor is mendacity, or Jessica is responsible. Both method we have now two responsible events, which contradicts Gordon. So the portray just isn’t on the windmill.
If the portray is on the cottage, then Charles is harmless (Sandy). However then Charles is telling the reality, so he is a gerontologist who began on the cottage. This may suggest Grant is mendacity, which is not potential. So the portray just isn’t on the cottage.
Subsequently the portray have to be at both the boathouse, the lighthouse, or the mansion. This implies Karen is mendacity, and is the thief.
By David’s assertion, we all know that the portray just isn’t within the boathouse. By Evelyn’s assertion, we all know that if the portray was within the mansion then the entrepreneur can be the responsible get together. However we additionally know that Karen is the decorator (Lyle), so the portray just isn’t within the mansion. Subsequently the portray is within the lighthouse.