Complex sentence: Jones summons the Kraken which traps the "Black Pearl", Jack discovering the heart is missing and attempts to abandon his crew, only to return when he sees the Kraken destroying the ship, wounding the Kraken with a net full of explosives.
Split into simpler sentences: Jones summons the Kraken which traps the "Black Pearl". Jack discovers the heart is missing and attempts to abandon his crew, but returns when he sees the Kraken destroying the ship, and wounds the Kraken with a net full of explosives.