In the last issue - Carnage 3, we saw Cletus Kasady, the original Carnage, back from the "dead." This issue starts with a flashback.
It starts with Cletus recalling his last memories - being torn in two by the Sentry in space. As Cletus remember's it however, he found it pretty funny that his legs were floating away. He then recalls the symbiote telling him that he needs to "sleep." He next awakens in a lab, where several tests are being performed. He also recalls that the "doctor" took samples of the symibiote.
Back to current time, Spider-Man, Iron Man, Michael Hall, and the Hall's three robot guys await Carnage. Carnage bursts out looking for Hall. Michael Hall however seems to be very calm and confident that his men can handle Carnage as he designed their suits using bits of the symbiote.
As a result this is what happens:
Carnage essentially gains control of Hall's men, killing them and merging their bodies with his causing him to become a large piece of dangerous "black."
Elsewhere, in the same building, Shriek and Doppelganger have found Dr. Tanis. Shriek demands to know where Carnage is. ( She used to have a thing with Carnage and considers him her boyfriend) Anyway, upon seeing Dr Tanis' symbiote arm, she scoffs at her. The arm tries to take control of her body, leaving the Doctor with no choice but to slice off her arm with a piece of glass. Shriek and Doppelganger just watch in amusement.
There are some pretty good fight scenes as Spider-Man and Iron try to take down the Mega-Carnage together. The final scene shows Shriek arriving at the fight scene with Doppelganger and Dr Tanis. Shriek however now has a third arm attached to her - Dr Tanis' symbiote arm.
This issue was pretty good. Consistent artwork, although I would have preferred it if Carnage didn't simply transform into that big hunk of black. Towards the end of the issue however it's a little easier to see his hands and legs.