The Banshee (Sean Cassidy) debuted in X-Men vol 1 #28 (January 1967).  At that point, he had been abducted by Factor Three and pressganged into service as the Banshee.  He went on to join the X-Men in 1975's Giant-Size X-Men #1.

Sean's previous history was originally established by dialogue rather than flashbacks.  The relevant issues are X-Men vol 1 #101-102 and Uncanny X-Men #148, with an elaborated version appearing in Official Handbook of the Marvel Universe #13.  Surprisingly, it wasn't until the late eighties that anyone started actually inserting flashbacks into his history.  There's only a handful of them, but they still raise some problematic continuity glitches.

CLASSIC X-MEN #16, second story
Sean Cassidy is victimised by corrupt Northern Irish police when returning home from a concert, but he is rescued by Maeve Rourke.  Over the following weeks, Maeve is torn between Sean and Black Tom.  Sean is injured by the corrupt police and misses a date with Maeve; Tom considers taking advantage, but decides against it and explains why Sean is not there.

X-MEN ANNUAL vol 2 #3, second story (various flashbacks)
Sean Cassidy is "a promising new agent of Interpol" and is keeping his power secret.  Assigned to guard weapons specialist Patrick Lipton, Sean fails to stop HYDRA from kidnapping him.  Lipton surrenders to HYDRA to prevent them killing Sean.

X-FORCE vol 1 #31, page 8 panel 3 (flashback)
Sean and Maeve marry, with Black Tom serving as best man. 

According to Uncanny X-Men #148, Sean is summoned back to Interpol duty shortly after the honeymoon and remains away, incommunicado, for months.  While he is away, Maeve discovers that she is pregnant with Sean's child.  She subsequently gives birth to Theresa Rourke Cassidy, who will eventually become Siryn and join X-Force.  Maeve is then killed in a terrorist bombing; Sean does not learn this until he gets back home.

CLASSIC X-MEN #26, second story (flashbacks)
While on an Interpol assignment, Sean meets Logan for the first time when their paths cross in a bar in Calgary.  [This is set "twenty years" before the framing sequence, which takes place at around the same time as X-Men vol 1 #120, the lead story reprinted in this issue.]

DEADPOOL vol 1 #2 (flashback)
Sean Cassidy and his partner Danny Peyer are sent by Interpol to break into the office of a mobster, Almadovar.  Sean is captured by Almadovar, but before he can kill Sean, Almadovar is himself murdered by Deadpool.  [Before you all start e-mailing me, Deadpool vol 1 is the second Deadpool miniseries.  The first one was called Deadpool: The Circle Chase.  The chronology of this flashback is garbled; in the present-day sections of the issue, Sean says that he left Interpol shortly after these events, following Maeve's death.  That contradicts all other accounts, which have Sean remaining with Interpol for some time afterwards and throwing himself into his work.  The flashback also contains a reference to Amahl Farouk being an active criminal at this point, which would place these events around twenty years ago, before Farouk died in the flashback in X-Men vol 1 #117.  All of this has the side effect of establishing that Deadpool has been active as a costumed mercenary for over twenty years, but that appears to be quite intentional on the part of writer Mark Waid!]

Sean then returns to Ireland and learns about Maeve's death, but not about Theresa's birth.

X-FORCE vol 1 #31, page 9 (flashback)
Sean visits Maeve's grave.  Black Tom approaches him, intending to tell him about Theresa.  Sean attacks him on sight, blaming Tom for failing to protect Maeve.  He breaks Tom's leg and then flies off in a rage.  Tom subsequently changes his mind and decides to conceal Theresa's existence; Sean does not meet her until Uncanny X-Men #148.

GENERATION X #10 (flashbacks)
"Nearly twenty years ago" (per issue #11).  In Paris, Sean investigates a serial killer whom Interpol are covering up.  He escapes other Interpol agents who try to arrest him.  Later, on a train, Sean is approached with further information by a mysterious man (who, unknown to Sean, will go on to become Magneto).  This is apparently only the latest of several meetings between the two.

GENERATION X #11 (flashbacks)
Sean follows the serial killer's trail back to his own home, Cassidy Keep.  It turns out to be the demented mutant Arkady Russovitch.  For political reasons, governments have covered up his murder spree.  However, Arkady now has a death wish and asks Sean to kill him.  Sean shoots Arkady, but the killer somehow survives and is taken away by the authorities, who transform him into Omega Red.  [No, it doesn't make much sense.  Don't ask.]

X-FORCE vol 1 #31, page 10 panel 2 (flashback)
After "years" away on various Interpol missions, Sean Cassidy finally returns to Cassidy Keep on an assignment to capture Black Tom.  They fight.  [The details are not revealed.  Theresa is away at a private school by this time, so Sean does not find out about her.]

GENERATION X #-1
Sean is now working as an NYPD detective.  While keeping surveillance on Harry Leland, Sean and his partner see the young Emma Frost being kidnapped by the Dark Beast.  Sean tries to rescue her.  Emma uses her telepathy to save Sean from the Dark Beast, but then sends him away with his memory erased, intending to form an alliance with the Dark Beast herself.  [This story is now a continuity minefield.  Emma is said to be 16 years old and living on the streets after being thrown out by her family.  This version of events, which Emma also gave in several other flashbacks in Generation X, is flatly contradicted by the version of her life set out in the current Emma Frost series.  There are apparently plans to explain this at some point in the Emma Frost book; however, it is hard to see how this story can stand in continuity without at least some significant revisions.  For present purposes, I assume the story takes place after events in Emma Frost published thus far, and that the references to Emma's age and homelessness have been retconned out.]

Not depicted: Factor Three kidnap Sean and pressgang him into service as the Banshee.

X-MEN vol 1 #26 (behind the scenes)
The Banshee is traditionally listed by official Marvel indexes as being behind the scenes in this story.  The basis is tenuous - issue #27 reveals that while the events of this story are ongoing, Cerebro detects the Banshee.

X-MEN vol 1 #27 (behind the scenes)
The X-Men detect the Banshee as a potential threat.

X-MEN vol 1 #28
Sean debuts as the Banshee and fights the X-Men.

Last revised: 24 September 2004