There is a murder in the works where a man is going to be killed by his cheating wife. The wife has hired a portrait painter, he is making a picture that will poison him when he looks at it! The painter explains that he will wear dark glasses when he paints it, so it can't kill him! He is also going to put rhubarb up his nose...
This is better than the Spanish Tragedy, more understandable. It reads like crazy science fiction.
It was based, apparently on a true crime of the time. There was an actual murder, recounted in Holinshed. Kyd just took the facts and ran away with them in the best way.