Greetings, fellow Arkhamites!
Looking for a few responses to gauge how others have played this particular card. As has been noted time-and-time again, FFG's strong suit is in the development of a very involved and highly thematic game, while occasionally missing the 'editing' function for their cards.
Museum Haunted ~ Headline: "...Investigators who destroy one of these Ghosts before the end of next turn may draw 1 Exhibit Item."
There are at least three interpretations (possibly more):
1. An Investigator defeats one Ghost (receives an Exhibit Item), and hides from the other Ghost, while another Investigator may defeat the other Ghost and also claim an Exhibit Item.
2. An Investigator may defeat both Ghosts and claim 2 Exhibit Items.
3. The Ghosts, while they both appear in the Miskatonic University Streets are treated ostensibly like the monsters encountered on the Rumor, The Terrible Experiment, whereby they're treated independently, so as in the first interpretation, the initial Investigator need not Evade the other Ghost.
Thanks in advance for your interpretation assistance.
The Professor