The biggest problems with conspiracy theories (ancient or modern) isnt normally any specific loose-end within the theory: that can usually be explained away somehow. The biggest problem is usually the plausibility of the conspiracys success. Beyond all the debate about exactly what planes flying into buildings can do, there is the question: could George W. Bushs government have organised a plot that was both so successful and so secret? And based on all their other attempts to organise things, the answer must be no. Similarly, Mohamed Al-Fayeds ideas on the death of Princess Diana need such widening groups of disparate conspirators involved to make it work as to become ludicrous.
I ended up thinking the same thing having just read an interesting article on an obscure Carolingian planctus (funeral chant): Fabre, Claudiane, Deux planctus rythmiques en Latin vulgaire du IXe siècle: I. Sur la Bataille de Fontenoy (841), II. Sur le meutre du sénéchal Alard (878). In La Chanson de Geste et le mythe Carolingien: Mélanges Réne Louis publiés par ses collègues, ses amis et ses élèves à l’occasion de son 75e anniversaire, 177-252. Saint-Père-sous-Vézelay, 1982. Alongside the famous lament on the battle of Fontenoy in 841, Fabre discusses a late ninth century text which laments the murder of a dux Adalard at the instigation of his wife. His ingenious solution is that the Adalard referred to is Adalard the seneschal of Louis the Stammerer and that the murder took place in 878, but was hushed up by the royal circle. All the evidence was destroyed, except for this text (two fragmentary copies of the planctus, apparently written by young pupils at the monastery of St Germain dAuxerre).
There are problems with some of the details of Fabre case, especially his following Ferdinand Lot in the very dubious assumption that the Adalard mentioned as tutor to Louis the Stammerer in 876 is the same one as the seneschal Adalard who fought at the battle of Fontenoy in 841 (most recent scholarship thinks that Adalard died in the 860s and his son is being referred to in the later texts). But the bigger problem is the simple question: could Louis the Stammerer and his supporters have suppressed mention of a death in 878? This strains credulity for several reasons.
First is the obvious point that Louis the Stammerer hardly looks the sort who could successfully carry out any policy: his short reign (877-879) has several humiliating climb-downs by him. Secondly, by the late ninth century history-writing was decentralised enough to make control of what was written very hard for rulers. In the late eighth century Charlemagne could mostly control what was written about Tassilo (though even then there are fissures enough for Matthias Becher, Eid und Herrschaft. Untersuchungen zum Herrscherethos Karls des Großen (1993) to point out the deceptions in the story). In 878 Hincmar was out of favour (and so not liable to take the party line), there were independent historians in the other kingdoms, lots of reports and letters from the papacy etc. Finally, Fabre never seems to put himself imaginatively in the position of the would-be conspiracy theorist. He argues, for example, that the lack of any mentions of Adalard in obits, necrologies etc, shows the success of the conspiracy. But its one thing to conceal a murder, its another thing to conceal a death. If you are trying to hide the fact that a 80-year old has been slaughtered in cold blood, then the obvious thing to do is to say: he died of old age, weve buried the body respectfully, good old Adalard, lets move along now. Similarly, Fabre wants to see the fact that the page with one version of the poem on has been largely cut away as proof of suppression of the text. Unfortunately for him, however, the second version of the poem is on the opposite page and is untouched. So either we have the worlds most hopeless censor, or the damage to the text has nothing to do with its embarrassing subject.
The problem is, if the poems not about a murder in 878, what is it about? I dont have a good answer to that one. The poem describes the murder of a dux Adalard at the instigation of his wife and that Louis knew she had Odo as a lover. The manuscript was written at St Germain dAuxerre at the end of the ninth century and the poem has verbal parallels to Angelberts poem on Fontenoy (although whether one can definitely prove the direction of influence is more debatable). I think its likely that the poem describes a real event rather than an purely imagined story and the reference to Louis strongly suggests a royal connection. The problem is, there are lots of Louis and Adalards and Odos around, who slip in and out of the sources without us knowing their whole careers. Even if the poem is definitely late ninth century, that doesnt help us much. Fabre assumes that the pupils were simply writing down a freshly composed planctus theyd heard, but earlier on hed already referred to the song about the seventh-century Bishop Faro of Meaux, which according to Hildegar of Meaux in 869, countrywomen were still singing. So even if the poem in its current form was composed or written down in the late ninth century, it may deal with events hundreds of years earlier. Louis could in fact be a Merovingian Clovis (in Latin these are the same name).
I dont have the time or patience to explore all the possible Adalards and Im not sure whether you could actually learn something definite even if you did. The careers of almost all early medieval noblemen are so obscure that its hard to know definitely how or when they met their ends, and anyhow the story may have been so distorted in the process of transmission that the actual facts were completely different (as in the Chanson de Rolands picture of Roncesvalles). But in the end, its still probably better to admit our ignorance then say we know something when we clearly dont. That way historical fiction lies…