As Fr Garnet, Provincial of the Jesuits in England, affirmed at the time, the plot to blow up the King, Queen, and the Three Estates of the Realm on the 5th of November 1605 was a most immoral and wicked plan (for one thing, one cannot willy nilly slay the innocent, along with those believed guilty of tyranny and oppression, by committing mass murder); not that that spared poor Father, since not only were the conspirators detected and hanged, but so was he - for not revealing what they had brought to him in confession, as well as for being a Popish priest.
Some Traditionalists may get a bit misty-eyed, and rather wish that Providence had permitted, rather than foiled, the careful firing of gunpowder beneath the State Opening of Parliament: but this is folly; ends justify not means. And further, as has been pointed out before, if the blast had been set off, even with the gunpowder "decayed", the huge explosion would have blown King James with his Lords and Commons to kingdom come, certainly (as recent tests have proven) - but almost as certainly, this would have not resulted in any Catholic restoration of merrie England: on the contrary, it would have most probably whipped up a Protestant vigilante frenzy, resulting in a reverse St Bartholomew's Day Massacre of English Catholics, one and all: for all would have been regarded as most barbarous conniving bloodthirsty fiends. Charles and his sister would have survived (they were not at the Lords), and easily eluded capture, and the Protestant succession to the throne would not have been harmed; but Catholics and Catholicism would have been even worse regarded in England thereafter than they were in reality.
To-day also marks that low point in English history, when James II lost his chance of keeping his throne by his pigheaded attempts to push his absolute authority and the cause of Catholicism when he had no hope of succeeding - for on this day in 1689 William III, that canny Dutchman, arrived in England, promising to preserve English (Protestant) laws and liberties; James found his power ebbed away, and he had to flee. If only James, the last of the Stuarts, had not been so stubborn and foolhardly as to alienate everyone!
As an amusing note, from the infamous Guy Fawkes, and the custom of making a ragtag "Guy" to burn at a bonfire on the anniversary of this day, came the expression "guy", originally for some oddly drest fellow, then for any man, and now, in the plural "guys" for any group of men, and even, as I myself use it, as an informal expression addressable to a gather of both sexes.