In the fourth-season opener, the crab-fishing fleet prepares to sail into the Bering Sea after some crucial repairs are made on the Northwestern, two new crewmates are trained on the Wizard and Johnathan's son Scott joins the crew of the Time Bandit.
A mechanical problem on the Northwestern prompts a risky repair, while a questionable crab count makes Sig flip out; some of the greenhorns on Wizard stand out because of their hard work; the crew of the Cornelia Marie is affected by Phil's poor health.
Sig and Edgar have a "last man standing" contest to see who can fish the longest without sleep aboard the Northwestern; Time Bandit's Capt. Johnathan has a close call; the crews of the ships begin to feel the pressure for a successful catch.
Tempers are short onboard Wizard and Northwestern; the Time Bandit has a dangerous electrical short; Phil's health worsens on the Cornelia Marie; Early Dawn hits high seas when its greenhorn falls asleep at the wheel.
As king-crab season comes to an end, the size of the crews' paychecks depends on their captain's skills; Capt. Johnathan has good luck fishing on the Time Bandit, but the same can't be said for the crew and boat; the North American rejoins the fleet.
As king-crab season comes to an end, the crew is dismayed when the pots come back filled with stinging jellyfish instead of the desired catch; the Cornelia Marie could lose Capt. Phil Harris for good; crew errors onboard the Northwestern add up.
As King Crab season draws to a close, the Northwestern is slowed by a deck accident. Meanwhile, the Cornelia Marie has an inopportune power outage; the North American does a "Hail Mary" play; and the Wizard and Time Bandit compete for a prize.
Opilio season begins, but a dual storm system threatens the patched-up Cornelia Marie and nearly costs Time Bandit two men; a medical emergency brings in the U.S. Coast Guard, but freezing spray endangers everyone.
A routine Coast Guard rescue becomes anything but; the Cornelia Marie heads in for repairs; fatigue causes errors on the Northwestern; a greenhorn locks horns with Capt. Keith on the Wizard; the Time Bandit looks for better grounds.
Capt. Johnathan joins the deck crew on the Time Bandit and has an accident while showing off his skills; the Northwestern crew angers Capt. Sig; Lenny from the Wizard barely escapes a huge wave; a North American greenhorn is hazed.
Storm waves damage the decks of the Early Dawn, North American and Northwestern; a rib injury causes Capt. Phil to cough up blood on the Cornelia Marie, but he refuses medical attention until his crew stops work in protest.
The Northwestern crashes through the ice pack; the Wizard heads out with a new greenhorn and hot tempers; Captain Phil's health leaves his future on the Cornelia Marie uncertain, so the crew try to make it on their own; a near-fatal mistake occurs on the Time Bandit.
Winter weather pushes Arctic pack ice south towards the fleet, forcing the Northwestern and the Wizard to deal with freezing spray; the crew of the Cornelia Marie suffers from "Bering Sea dementia" and Time Bandit's crew is close to a breakdown.
As the boats race to catch the last remaining quotas, ice and equipment issues take precedence, and a Time Bandit crewman makes a near-fatal mistake working the hydraulic system; an ominous message sends the men back to port.