the logical link expressed by the missing words:
-conséquence (so, that's why, therefore)
-opposition (but, however)
Who killed Mrs Dennis? She had no money (so) her niece had nothing to gain from the death of her aunt. It could be Mr Johnson, her neighbour, (because) he was away when she was stabbed. (But) he may have hired someone to do the job for him while he was in London. And why would he have done that? (However), he had once said he would be glad to see her dead! There is Jack Nelligan. By killing her, he would have taken his revenge (therefore) she had played a dirty trick on him a long time ago. Well, this is a tricky case indeed.