This question is a follow-up to How has knowledge of the Ur-Hamlet evolved over the centuries? in which we learned about how it first came to be postulated that Shakespeare's Hamlet was based on an earlier story of the same name by a different writer. Another question naturally arising out of this is, given the assumption that there was an Ur-Hamlet, whose text is now lost, what can be deduced or at least solidly guessed about its content? Even though the text itself is lost, references to it remain in other pieces of literature, and perhaps there's more evidence to be found in other Hamlet-like stories from around the same time. I don't need certain proof, but clear evidence based on serious studies would be good, not just pure guesswork.
The assumption that an Ur-Hamlet existed is based on a passage from Thomas Nashe's preface to Robert Greene's Menaphon. Nashe writes (bold emphasis mine),
It is a commom practise now a daies amongst a soft of shifting companions, that runne through euery arte and thriue by none, to issue the trade of Nouerint whereto they were borne, and busie themselves with the indeuors of Art, that could scarcelie latinise their necke-verse if they should haue neede; yet English Seneca read by candle light yeeldes manie good sentences, as Bloud is a begger, and so foorth: and if you intreate him faire in a frostie morning, he will affoord you whole Hamlets, I should say handfulls of tragical speeches. But ô griefe! tempus edax rerum, what's that will last alwaies? The sea exhaled by droppes will in continuance be drie, and Seneca let bloud line by line and page by page, at length must needes die to our stage: which makes his famisht followers to imitate the Kidde in Aesop, who enamored with the Foxes newfangles, forsooke all hopes of life to leape into a new occupation; and these men renowncing all possibilities of credit or estimation, to intermeddle with Italian translations: (…)
Greene's Menaphone was printed in 1589 and based on the topicality of Nashe's comments, he may be referring to a play called Hamlet from 1588 or early 1589. Thomas Kyd may have been that play's author (or one of its authors). However, Nashe's comments don't tell us much about the play's content other than that it may have been inspired to some extent by Seneca. (Jasper Heywood's translations of Seneca in the 1560s probably contributed to the emergence of the revenge tragedy as a genre a few decades later; Thomas Kyd's The Spanish Tragedy (1592?) established the genre.)
One of the things we know about this play is that it had a ghost. Thomas Lodge writes in Wit's Miserie (1596):
(…) & looks as pale as the Visard if ye ghost which cried so miserally at y Theator like an oister wife, Hamlet, reuenge: (…)
According to Lukas Erne, there is very little that can be inferred from the early editions of Shakespeare's Hamlet, with the possible exception of certain passages in the first quarto of 1603 ("Q1", long considered a "bad quarto") that differ from the second quarto ("Q2", 1604) and the first folio ("F1", 1623). In these passages, Hamlet's mother Gertrude is informed about Claudius's plot against Hamlet (i.e. sending him to England with a letter telling Hamlet should be killed) and is clearly on Hamlet's side, whereas in Q2 and F1 she is a much more ambiguous figure. This more sympathetic treatment of the queen is something that Q1 has in common with Belleforest's Histoires tragiques, which may have been Kyd's source. (Belleforest's novella, by contrast, didn't feature a ghost.) However, Shakespeare may also have used Belleforest as a source, so it is also possible to hypothesise that Q1 represents an older version that he later rewrote and that he changed his mind about Gertrude in the process. (The weakness of this hypothesis is that Shakespeare does not appear to have proofread his own plays and thus not have cared much of how they appeared in print.)
This seems to be the extent of what is known about the content of the Ur-Hamlet.
- Erne, Lukas: Beyond the Spanish Tragedy: A Study of the Works of Thomas Kyd. Manchester University Press, 2001.
- Greene, Robert: A Critical Edition of Menaphon by Robert Greene with the Preface by Thomas Nashe, edited by Ardelle Cowie Short. Yale University, 1977.
- Lodge, Thomas: The Complete Works of Thomas Ledge. Volume Fourth. 1883.